THE study of varieties in the genus Nassa has achieved one great object, it has taught us the whole details of the plan on which the external ornamentation of shells has been elaborated. The whole of the variation, from the smooth shell to the most distinctly sculptured examples, is plainly to be seen as effected through almost imperceptible gradations.

An attempt might be made to show the lines of divergence by means of a diagram, but in all the instances in which this has been done in other branches of Natural History the results have not been satisfactory.

Neither a tree-like form nor any genealogical chart could be made to represent varieties in anything like the ramifications in which they occur in Nature, nor could we hope to succeed in such an undertaking without being able to procure a very large addi tional series of species such as would enable us to follow more closely the missing links in the scale of affinity.

For the most part, I do not regard a peculiar character possessed only by a single specimen as constituting a "variety." Even "intermediate links" between allied forms are generally represented in my series by two, three, or more, closely similar specimens,

Variation through the whole kingdom of Nature is the rule and not the exception. It is the prejudice exhibited by Scientists, against so much that is clear and distinct, that creates confusion. If studied as it exists, the whole group is manifestly developed, step by step, and we see the wisdom, power and beneficence of the Maker. We see the qualities implanted in these creatures to enable them to construct their houses with consummate skill, and to ornament them, either plainly, in Quaker fashion, or most elaborately in external sculpture. Men are constantly inventing theories to account for changes occurring in Natural History objects, and everything must bend to suit their special hypotheses.

Only one arrangement can be correct, and we have only to examine the materials and gain an extensive knowledge of the sections in each division to be convinced of this truth.

The greater part of the works on Natural History are written in the closets of the authors, who both theorise and copy to a large extent; but, unfortunately, they copy errors as well as facts.

The study of variation has opened up a subject so vast in its dimensions that the mind almost shrinks from the task of estimating it. In every direction variation extends, in every way variation seems to ramify, until we gaze and wonder if there be any end.

Instead of 200 Species, at least 3,000 Varieties are before me, and the end appears nearly as far off as ever. Taking a careful survey of the shells under consideration, and noting more particularly the common forms and the changes presented by them, we are enabled to form an estimate of the enormous number likely to be met with, if we persevere in our work of collecting varieties. Species are and have been made by men in their ignorance. Had they known the alliances, it would have been impossible for them to have committed such mistakes as are to be found in conchological books. Species have been and still are the ultimatum of scientists. It appears to me that they have an instinctive horror of the nameless. Lamarck described the Nassa subspinosa from shells that were subspinous, not then knowing that there were carinated, costated, muricated, and smooth

varieties of it. At least six good (?) species have emerged from the varieties of Lamarck's shell: N. lyrata, Marrat, is the lyrate form; N. tricarinata, Lam., is the carinated form; N. sculpta, Marrat, is another; N. sistroides, Neville, N. trinodosa, Smith, and N. corticata, A. Ad. Another variety occurs showing a close affinity with the N. muricata, Quoy and Gaim., and the shell figured in Reeve's Conchologia Iconica as the N. vibex, Say, is a spiny form. Some of the shells from Ceylon are very closely connected with varieties of the N. Gruneri, D'k'r., and others with smoother ribs to the N. Jacksoniana, Quoy and Gaim.

In the preface to Wood's Catalogue of Shells, published in the year 1828, we find the following remark: "It has, therefore, been the endeavour of the author, in the absence of larger and more costly publications, to supply their place by a work which will incorporate in one volume figures of all the known shells." From the statement here quoted the number of shells known to conchologists at this date amounted to about two thousand. A little more than fifty years have elapsed, and we find that the numbers have increased to at least thirty thousand. Suppose we recommend the study of a single genus to each of our conchological students; if the success attending their efforts be in proportion to those resulting from the study of the Nassæ, before this century expires we will have at least five hundred thousand shells. We may name these shells and describe them as distinct, but they will not be so after we have finished; on the contrary, we may adopt another plan and name them varieties, but the same objection continues; the variety we have named as coming from any locality will be found to differ from the shells brought up from the same ground by the next haul of the dredge. It is a very disagreeable task to be compelled to state that the starting point of the systematist, upon which the whole fabric is built up, is wrong, and the whole of the deductions drawn from this source are erroneous; nevertheless, I am compelled to utter that which I believe to be strictly and unquestionably true. I cannot expect the conchologists, who are totally unacquainted with the materials upon which I have based my deductions, will be found to coincide with my views. If they had studied the genus

Nassa and had obtained a knowledge of the whole of the species either figured or described in it, they could not by this plan follow the intricate passages revealed by the study of variation. It is not by the intimate knowledge of the species themselves that these facts are elicited, but it depends upon a knowledge of the innumerable intermediate forms which diverge from them in every direction as to how these deductions are to be drawn. The conchologist and I are dealing with two distinct subjects, intimately connected, but differing materially in the result obtained; the one is confined to the number of the shells figured and described, while the other wishes to embrace every variety occurring in creation, most of which are neither figured nor described.

When the whole series is spread out, in lines in their trays these shells forcibly remind us of the people standing round a race-course when the horses are running. The different sizes in height and breadth, the different coloured clothes, the marked differences in form and feature, and the various casts of countenance, all exhibit, in proportion to the difference in the size of the objects compared, just such an amount of variation as we find in the varieties of the Nassæ.

The lines of descent from the largest to the smallest forms are often distinctly indicated, notwithstanding the large number of variable shells intervening between the first form and the last.

Shells may be selected, in series, that will show a clear line in the descending order from Nassa glans, Linn., to Nassa incrassata, Müll., variety glaberrima; but if these varieties are examined in the order in which they appear to fall naturally, then we find that an off-shoot takes place at the junction of the varieties of Nassa mucronata, A. Adams; another with Nassa Marratii, Smith; a third with the Nassa gaudiosa, Hinds, etc. Another of these lines may be started with the Nassa trifasciata, Gmel.; but in this case, instead of tracing smooth shells, as we did in the last, the shells would pass into coronated, costated, and cancellated forms before returning to a similar small form to that with which we started. Most of the costated varieties such as Nassa nodifera, Powis, the cancellated varieties such as Nassa marginulata, Lam., and the elongated series

such as Nassa sequijorensis, A. Adams, would form a part, and a very important part, in this line of descent. One of the series of shells in which the most gradual and almost imperceptible grades of variation takes place is that commencing with the Nassa turrita, A. Adams, and ending with a shell very little larger than Rissoa costata, viz., the Nassa costulata, found fossil in the Miocene of Bordeaux. This series includes the Nassa limata, Chemnitz; prismatica, Brocchi; lucida, Marrat; proxima, striata, and versicolor, C. B. Adams; denticulata and rufocincta, A. Adams; crebristriata, Carpenter; annellifera, Reeve; ambigua, Montague, etc.

In a long series of forms, commencing with shells representing the largest specimens in the genus, these can be traced with unerring certainty into others forming the smallest examples known to exist; again, the broadest varieties can just as easily be connected with others that are the narrowest examples in the group; and every grade of difference throughout the long lines of progressive variation is distinctly seen.

In a case of the shells having smooth forms, such as N. glans, Linn., the varieties may not be all smooth specimens, but they may vary into costate and even cancellated examples. Again, instead of there being a uniform rate of variation of thickness observable, one set will be almost transparent or thin and hyaline, and another thick and quite opaque. The sculpturing is in many cases confined to the upper whorls, but we find shells in which the pattern is commenced on the top gradually spreading in successive development until it covers the whole shell; in one case it may form smooth unsculptured ribs, or in another it may diverge into any of the forms of sculpture we meet with in other groups of shells. The tip of the spire may be of the same colour as the remaining portion of the shell, or it may vary into almost every shade of pink, rufous, brown, purple, or almost black.

The shells used as starting points are not intended as distinct forms, nor are they anything more than varieties chosen for the purpose of illustrating the subject of variation through a number of its ramifications. All the divisions marked with a dash will be found to assimilate with each other in some of the varieties