Sea Lilies. 1 1 



unarmed, its liberty giving it a greater choice of food ; and 

 the disk is comparatively unprotected. 



. At first I had some doubt as to the propriety of making 

 this species the type of a new sub-genus, and any one of the 

 above characters would certainly not have afforded sufficient 

 grounds ; but all these characters taken together form a remark- 

 ably compact assemblage, which places Neoceinus in a directly 

 intermediate position between Cenoceinus and Comatula. 

 Comatula becomes free, and gains its liberty by a rupture of 

 the stem between the representative of a cirrhigerous joint and 

 the upper joint of the only developed inter-node ; it has few 

 arms, provided with syzigies to the end; its disk is usually 

 nearly naked ; and its mouth is unarmed. 



Here then we have apparently three marked types, the two 

 last partaking in different degrees of the same form of devia- 

 tion from the first, and from the general character of the main 

 body of their order. In such a case one would certainly be 

 strongly inclined to trace all the closely allied forms to a com- 

 mon ancestry, and to attribute each special deviation to the 

 sum of an infinite series of minute variations. And yet the 

 life history of the Crinoids does not seem as a whole to give 

 unqualified support to the Darwinian theory. Certainly one of 

 the strongest points in this hypothesis is the production of 

 variation by " natural selection/' From the beginning almost 

 all the Crinoids have been permanently stalked, and entirely de- 

 pendent for the fertilization of their eggs upon particles derived 

 from any source, and scattered at random in the water of the 

 sea. Under these circumstances the principle of natural selec- 

 tion cannot come into play, and we should anticipate that a 

 group so circumstanced, would vary much more slowly and to a 

 less marked degree than its locomotive cotemporaries. Now it 

 so happens, that far from this being the case, the Crinoids 

 during the lapse of geological time have run through a wild 

 series of modifications, while the locomotive Echinoderms, from 

 the lower Silurians upwards, do not differ very greatly, at all 

 events in external form, from those of the present day. 



Plate (see frontispiece). — Pentaceinus (Cenoceinus) Gaput- 

 Medusce (Mill.) a, portion of the upper part of the stem; 

 b, the end of one of the stem-cirrhi; c, a portion of the stem 

 near the base ; d, a part of one of the arms, showing the 

 arrangement cf the pinnules. 



