tries outside of the United States. Naturally, from the contiguity of Canada, the largest number of those foreign members reside there, the list showing 230 names of residents of Canada. This number is larger than the total membership of the Royal Society of Canada, which, however, limits its membership. But it is small in comparison with the total membership of the Association, although not insignificant in view of the fact that no meetings have been held in Canada since the last Toronto meeting thirty-two years ago. After the meeting of 1889, the next following list contained 85 names of members and fellows resident in Canada. While only seven of these 85 persons now survive as members, the present Canadian membership of 230 indicates that accessions have been increasing, and doubtless there will be further increases as a result of the meeting about to be held. The place of the meeting is also a reminder that the Geological Society, at the time of the last meeting in Toronto, took a step toward organization as an independent body, which was the beginning of a movement that has eventually contributed to the remarkable growth of the Association. The recently issued volume shows that in addition to the large membership of nearly 12,000, there are now 93 affiliated and associated societies, most of which have been organized since 1889.

NORMAL SCHOOL BUILDING, TORONTO, Nov. 15, 1921

A. F. HUNTER

SCIENTIFIC BOOKS

The Life of the Pleistocene or Glacial Period. By FRANK COLLINS BAKER. University of Illinois Bulletin, vol. XVII., No. 41; June 7, 1920, iii, 476 pp. 8, pl. 1-57. Urbana, Illinois.

This portly volume is divided into two parts, the first including beside a historical summary of preceding researches an account of the postglacial geology and life of the Chicago area, followed by a résumé of our present knowledge of the postglacial life of the entire glaciated region of the United

States and Canada. Each locality investigated is taken up separately, its stratigraphy and fossil content described and listed, and at the end of each chapter the collected data are summarized.

In the second part the life of the interglacial intervals is discussed and the species of plants and animals listed from data furnished by an indefatigable search of all available literature.

The difficulties attending the reduction to a common nomenclature of the records extending over many years, can easily be understood and the author frankly acknowledges that in some cases his judgment may have been at fault, but such instances do not materially affect the general conclusions and are inevitable in any such bringing together of scattered data of varying degrees of authenticity. The volume concludes with a . bibliography of forty-five pages, covering the literature from 1846 to the date of publication and an ample index. Among the plates are interesting maps showing the fluctuations of the geographical features of the Chicago area and the region about Toronto, as well as the extensions at numerous periods of the continental ice sheet. It would have added to the convenience of those who use the volume if legends had been added to the plates, obviating the necessity of turning back in each instance to the printed explanation.

Much of the work, and presumably of the most carefully observed and valuable part of it, is the result of field work prosecuted by the author. The labor involved in the search for and correlation of the data in the literature was evidently prodigious, and reflects credit on the industry and patience of the author. His work in bringing together in orderly shape the data bearing on his subject will be a boon to all later students of the American Pleistocene. We may be permitted to regret the instrusion in a scientific work of a few of the "simplified spelling" futilities; we really of not to imply that thot renders either the sound or the meaning of the word thought.

WM. H. DALL

SPECIAL ARTICLES

THE EGG-LAYING HABITS OF MEGARHYSSA (THALESSA)

DURING the summer of 1921 I had frequent occasion to watch the females of the beautiful large Ichneumonid Megarhyssa (formerly Thalessa) in the act of ovipositing into the trunk of a decaying maple tree at Mendham, N. J. In looking over the literature on the subject, I find that this process, though often described and commented upon, does not seem to have been fully elucidated so far. There are at least two facts that have escaped attention of observers, namely first, that the ovipositor is always brought into a position at right angle to the bark directly behind the thorax of the insect and is held here in position by the hind coxae, allowing only upward and downward movements but no lateral excursions. It is only under this condition that one may correctly say that the insect "makes a derrick out of her body" (Comstock). The second point is, that the remarkable extensile membranous sac or disc into which the ovipositor enters with its basal part to allow of its being temporarily shortened, is not only formed twice, at the beginning and at the end of the process, but at the beginning receives also the sheaths into its interior, which are freed when the membrane collapses, as two separate loops, while at the end of the process, when the membranous sac forms again, the loops of the sheaths do not re-enter it, making it possible that one can tell whether the insect is just beginning or just ending operations.

It appears that the extensile membranous sac has been seen first and correctly interpreted by J. Quay, who, however, does not mention the loops formed by the sheaths. The most complete and accurate account is given by C. V. Riley, who describes the loops formed by the sheaths, which, as he correctly stated, do not enter the wood. But Riley is in error in his statement that the sheaths "have not followed the ovipositor within the membrane"; in fact they do 1 American Entomologist, Sept., 1880, Vol. III., p. 219.

2 Insect Life," Vol. I., 1889, p. 168 ff.

so at the beginning of the process. According to Riley the sheaths make "a larger and larger loop on one side of the body3 or even a valve on each side," and he figures the ovipositing insect with ovipositor and sheaths on one side of the body which is quite impossible. In the same figure, otherwise excellent, the ovipositor is drawn at a certain distance behind the end of the thorax, while, as I have stated above, it is held by the hind coxæ. Riley criticizes the previous illustrations (Blanchard, Wood), which figure Thalessa (Rhyssa) as ovipositing into insect larvæ which she never does.

More recently, Comstock gives an illustration possibly adapted from Riley as it figures almost exactly the same stage in the egglaying process, and especially as it continues both Riley's errors in figuring the ovipositor at a certain distance behind the thorax, and on one side of the body. The wings are drawn as if held vertically; the antennæ held farther upward than in Riley's picture. The vertical position of the wings is preserved in Kellogg's and Lutz's figures. Kellogg's figure is almost identical with that (presumably older one) of Comstock but apparently redrawn as to details; the error of drawing the sheaths both on one side of the body has here been eliminated. The figure in The New International Encyclopaedia (2d edit., 1915, article "Ichneumon fly"), is adapted from Riley; the antennæ, however, are here drawn as if directed vertically upward-perhaps to save space. It should be noted that the egg-laying insect holds the antenna forward and often downward, touching the bark. This figure also shows both Riley's errors which I have commented upon. A new illustration is given in Lutz's "Field Book of Insects" (1918; Pl. LXXXVIII., p. 413); this illustration was, as Dr. Lutz tells me, not drawn from nature but combined from illustrations and a specimen they had. This picture is the first one in a long time to show a different stage in the process than that 3 Italics mine.

figured by Riley, and the membranous disk is shown correctly with the sheaths inside, corresponding to the beginning of the boring process. But the position of the abdomen is impossible; indeed at this stage, when the disk is formed, the abdomen is held not only vertically but even bent forward to some extent above the thorax; and at no time during the whole process is the ovipositor inserted as far behind the insect as drawn by Lutz. Like Comstock, Lutz shows the wings in a vertical position and the antennæ are held obliquely upward which is possible but not characteristic. Mention should be made that Riley too, already gave a picture, undoubtedly from a preserved specimen, of the extended membrane, the two sheaths just leaving it, as would be the case as soon as the membrane begins to collapse. This illustration shows very well how the ovipositor at the beginning of the process is held in a vertical direction by being sunk into a ventral furrow of the abdomen, which renders its basal portion quite invisible.

It becomes a matter of interest that, of many authors commenting on such a familiar insect as our large, long-tailed ichneumon fly, and on its oviposition, only comparatively few have watched the process long enough to verify its details, and that, in fact, some of these details have never been clearly established though Megarhyssa is common in many localities. Does not this indicate that we have been neglecting the ecological for the systematic aspect of entomology?

high pressure from a small nozzle into a long narrow throat. The nozzle opening is made sufficiently small that the pressure of the vapor

6 mm:

in the boiler, instead of being practically limited to 2 or 3 millimeters, as in the case of the ordinary vapor pump, may attain a value of 75 millimeters or more depending upon the heating. The efficacy of this arrangement was first pointed out by Stimpson. The evac1 Washington Acad. Sci. J., 7, pp. 477-482, Sept. 19, 1917.

uation is completed through the fine stage, B. In this unit a portion of the high-pressure vapor from the central tube is allowed to expand to a low pressure through one or two small openings into the inverted cup, C. This vapor then escapes freely into the large water jacketed tube and gives the conditions essential for high-speed exhaustion.

It has found that the high-pressure stage operating alone, without assistance from the low-pressure unit, will produce a high vacuum. The speed of the high-pressure unit by itself, however, is very much less than that of the combination, which possesses a speed comparable with that of a single stage pump of equivalent proportions.

The advantage of the combined units, of course, lies in the fact that such a pump will function in a perfectly satisfactory fashion with a very ordinary fore-vacuum. A mechanical pump capable of reducing the pressure to 2 or 3 millimeters is satisfactory, or even a water aspirator which will give a vacuum of 20 millimeters can be used if nothing better is available.

With regard to the construction of the pump perhaps a little may be said. Glass possessing a low coefficient of expansion such as Pyrex or Corning G702P glass must be used in making it, as otherwise one will almost certainly experience the rather annoying inconvenience of having the boiler crack upon application of the heat. The size of the pump can, of course, be varied considerably, but the general proportions of the parts given in the drawing are found to be very satisfactory. In the pump from which the drawing was made the mecury boiler has a diameter of 90 millimeters and the other dimensions were reduced proportionately. The dimensions of the jet and throat which have been found to work well are indicated in the enlarged sketch of this part. The diameters given apply to the tube openings. The thickness of the nozzle wall should be as thin as is consistent with

reasonable strength. The two small openings which serve to furnish a supply of vapor to the upper unit are about the size of ordi

nary pin holes and are located on opposite sides of a small enlargement in the central tube. The joint between the lower end of the water jacket and the body of the pump is made water tight by binding it tightly with strips of thin rubber. There is some advantage in having a slight constriction where the mercury return tube is sealed to the boiler as the presence of a constriction here tends to preserve the equilibrium of the mercury in the return tube.

The mercury in the boiler should be about 2 centimeters in depth at the center and ordinarily, with a properly adjusted flame, it will evaporate without serious bumping even at the higher pressures. The height of the mercury column in the return tube indicates the vapor pressure in the boiler and the pressure required for satisfactory pumping depends entirely upon the fore-vacuum. There is no harm, however, in running the vapor pressure up as high as the length of the return tube will permit if this be necessary to enable the pump to function.

PALMER PHYSICAL LABORATORY, PRINCETON, N. J.

E. H. KURTH

THE AMERICAN CHEMICAL SOCIETY

(Continued)

DIVISION OF AGRICULTURAL AND FOOD CHEMISTRY

C. E. Coates, Chairman

T. J. Bryan, Secretary

The testing and grading of food gelatins: CLARKE E. DAVIS AND EARL T. OAKES. Loeb's recent work on gelatin is briefly discussed and Bancroft's objections to Loeb's conclusions on the basis of the insolubility of gelatin as based on surface tension measurements by Slobeki are shown to be in error. Methods for determining gel strength and viscosity are given and the effects of various factors affecting these properties are discussed with data. Data on the causes for discrepancies between grading gelatins by gel strength tests and by viscosity measurements are given. Gelatins submitted by the manufacturers as examples in which gel strength does not parallel viscosity are shown to be classified alike by gel strength and viscosity measurements under the methods described.

Active chlorine as a germicide for milk and

milk products: HARRISON HALE AND WILLIAM L. BLEECKER. The increasing and satisfactory use of active chlorine as a germicide for water suggests the possibility of its use for milk and milk products. Numerous bacteriological tests show a reduction in number of bacteria in general proportional to the amount of active chlorine present. Chlorine water, sodium hypochlorite and calcium hypochlorite solutions were used on milk and ice cream in dilutions varying from 1 part of active chlorine to 1000 parts of milk to 1 part to 100,000. Chlorine water in 45 minutes produces practically the same results that sodium hypochlorite does in 11⁄2 hours and calcium hypochlorite in 19 hours.

The inadequacy of analytical data: H. E. BARN

ARD.

The chemistry of leavening agents: CLARK E. DAVIS AND D. J. MAVEETY.

Availability of salts in soils as indicated by soil colloids: N. E. GORDON. Iron, alumina and silica gels were prepared in the purest possible condition and shaken with various salt solutions until equilibrium was established. The maximum adsorption was determined. Then by a series of washings it was found in what way and to what extent the adsorbed salt became available for plant food. Furthermore, a series of experiments showed that the hydrogenion concentration plays a very important rôle in the availability of salts which are held by soil colloids.

The effect of pectin, acid and sugar on the character of gels: C. A. PETERS AND R. K. STRATFORD. Pectin extracted from apple pumace by water was used and a standardized method for making gels in 10 c.c. portions was developed. Acidity of 0.3 per cent. was necessary for gelation and acid above 0.3 per cent. did not increase the stiffness of gels. As the per cent. of pectin was increased the amount of sugar had to be increased to make the stiffest gel; with a certain per cent. of pectin less sugar makes a softer gel, an increase of sugar makes a stiffer gel while a further increase of sugar makes a gel less stiff. The character of the gel depends upon the hydrolysis of both the sugar and pectin.

Nutritive studies of the Georgia velvet bean, Stizolobium Deeringianum. III. Supplementary relationship of whole and skimmed milk to the hulled seed and the whole plant: J. W. READ AND BARNETT SURE. An earlier paper1 in this series of studies

1" Biological Analysis of the Seed of the Georgia Velvet Bean, Stizolobium Deeringianum," Jour. Agr. Res., Vol. XXII., No. 1, pp. 5-18.

on the nutritive value of the Georgia velvet bean showed that the raw bean is injurious to rats. If the ration is supplemented with a liberal supply of whole milk, rats grew at a rate even more rapid than normal, and three generations were successfully reared on this diet. Inasmuch as previous work had shown the velvet bean to be quite rich in the fat-soluble vitamine, experiments employing skimmed milk instead of whole milk and replacing the dextrin by starch were tried, but rearing of the young in two cases was not successful. In the case of the whole plant, however, a healthy and vigorous third generation was secured on such a simple and poorly constituted diet as that composed of 40 per dent, velvet bean hay (ground whole plant), 60 per cent. starch, and a liberal supply of skimmed milk.

Nutritive value of the Georgia velvet bean (Stizilobium Deeringianum). (a) Supplementary relationship of leaf and the hulls of seed. (b) Nutritive value of the whole plant: BARNETT SURE AND J. W. READ. Our previous work2 on the nutritive value of the Georgia velvet bean showed the seed to be abundant in the fat-soluble vitamine, but deficient in protein, salts, and the water-soluble vitamine. In this study we have found the leaf to be abundant in the water soluble and an efficient carrier of salts. The hulls, however, possessed no supplementary value to the seed, and they interfered with the utilization of the fat-soluble vitamine in the seed, as did also the velvet bean hay. Autoclaving the hulls for two hours at 15 pounds pressure did not change their disturbing effect. The data secured suggest that the interference with the utilization of the fat-soluble vitamine may pos sibly be due to indigestible celluloses.

Calcium chloride as a mineral supplement in the ration. (Preliminary report): J. W. READ AND BARNETT SURE. The literature contains the results of experiments conducted by several investigators within the last eight or ten years on the benefits derived from the addition of small quantities of calcium chloride to the ration. We considered it of possible value to check up on some of the results which have been reported, and have in progress certain experiments with rats, in which cotton seed meal constitutes 35 and 50 per cent. of the two basal rations which receive calcium chloride additions varying from 0.60 to 16.00 grams of the tetrahydrate salt per kilogram of ration. The rations receiving calcium chloride are compared to the controls free from salt additions, and to rations receiv2 Jour. Agr. Res., XXI., No. 9.