292 TAYLOR : ON THE VARIATION OF MOLLUSCA. 



pressly denies that species as usually understood exist, he 

 nevertheless not only retains the names of a number of the 

 species already described — or forms as he prefers calling them — 

 but adds a number of fresh ones to the list. 



I have thus shown that I should require structural difference 

 in species, but varieties, with which we are at present more 

 immediately concerned I would confine to external modifications; 

 thus I would propose to regard as varieties worthy of a definite 

 name the extreme divergencies — if sufficiently marked — of size, 

 texture, color, markings, shape and the difference in proportion 

 or the exaggeration or restriction of the development of special 

 parts of the shell. 



It is I believe generally conceded that differences of form 

 are relatively of more importance than variations in colour, 

 markings size or sculpture. 



Thus in attempting to arrange the varieties of that protean 

 shell Liinncea peregra — of which I have myself catalogued near 

 300 names that have been bestowed upon it, either specifically or 

 varietally by various authors, but which are probably reducible 

 by a careful and attentive comparison to a much more reason- 

 able and moderate number — I would regard as of first im- 

 portance the form-variations, as for instance the oblong speci- 

 mens which have been named var. oblonga by Jeffreys, the 

 globose form which has received amongst other names that of 

 laaistris, the inflated variety which has been called obtusa, or 

 the varieties burnetii and involuta which are remarkable mainly 

 for intortion of the apex. Primarily separated in this way, we can 

 readily understand that the albine mutation for instance, is liable 

 to occur in any of what I may term the primary varieties. To 

 distinguish this color mutation, only by its special name Candida, 

 would be to lose sight of the other and more important character 

 — its form. It seems to me therefore to be necessary to adopt 

 in cases like these, a modified and somewhat extended system 

 of nomenclature, to enable us to refer with terseness and pre- 

 cision to these subvariations, as they must be termed under this 



J.C, v., April, 1888, 



