Anatomy o/" Comatula. 209 



fact also I have indicated in Par. 15 of the First part of my 

 Memoir. 



I expect to be able to prove that the Crinoidea have scarcely 

 any thing in common with Echinoderms generally as to plan 

 of structure, and that their developmental history differs 

 essentially from that which is now regarded as characteristic 

 of that group. In fact, as Prof. Semper remarked to me, a 

 Crinoid might almost be considered a more highly organized 

 Polype. In its early state the digestive cavity has but a 

 single orifice in the centre of the oral disk ; and the animal 

 then exhibits an absolutely perfect radial symmetry. The only 

 departure from this symmetry in the adult Crinoid arises 

 from the elongation of the digestive cavity into an intestine, 

 the anal termination of which appears on the oral disk, bearing 

 in Comatula an unsymmetrical plate, which belongs to the 

 " perisomatic skeleton "*. The " radial skeleton," with its 

 ligaments, muscles, and nerves, and the complicated vascular, 

 respiratory, and generative systems contained in the arms, 

 all have such an exact radial symmetry, that to affirm that 

 Crinoids are modified Annelidans, merely because the " pro- 

 embryo " which carries about the true Crinoid-germ has some- 

 what of an Annelid form, seems to me about as scientific as 

 it would be to describe Man as a Radiate, because the villous 

 chorion, which furnishes nutriment to the true Vertebrate 

 embryo, is globular. If the type of the Nervous System goes 

 for any thing, and this nervous system in Comatula is what 

 I affirm it to be, its disposition, from its very first appearance, 

 is as distinctly radiate, as the disposition of the nervous system 

 in the Articulate and Vertebrate subkingdoms is bilaterally 

 symmetrical. 



Doubtless I shall be charged in this instance, as I have been 

 in others, with an undue preference for older to newer ideas, 

 and with an indisposition to avail myself of the light thrown 

 by developmental history upon the affinities of animals. I 

 only ask, however, a suspension of judgment until I shall have 

 published the facts which have been in my possession for more 

 than ten years past, and which I only want an interval of 

 leisure concentrated upon the subject to present in a com- 

 plete and systematized form. 



* See par. 84 of the first part of iny " Researches." 



