239 



Neither time nor space permits me to enter on a detailed discussion of 

 the phylogeny of Echinoderms. I must content myself with stating 

 my perfect agreement with Ha I her's views on this matter ') ( I would 

 only call attention to the difficulty pointed out already by Bury 2 ) that 

 no stage of fixation occurs in the embryogeny of Echinoderms, excepting 

 the Crinoids; the fixation of Brachiolaria 1 by means of the sucking disk 

 is, as hinted at by Bury, evidently a secondary adaptation, which hardly 

 counts in this connection ). Consequently 1 am decidedly opposed to 

 the theories of the ancestry of Kchinoderms more recently set forth by 

 A. 1 1. Clark 3 ) and J. E. V. Boas 4 ) -- not to mention that of Simroth 5 ). 

 In my memoir on the development of Crinoids I have objected to some 

 few points in the theory of Clark who maintains the barnacles to be 

 the ancestors of Echinoderms: but otherwise I do not think this theory 

 more worthy of a refutation than that of Simroth, deriving the Echino- 

 derms from Myzufsloma! My few counter-remarks to some of the inter- 

 pretations of Crinoid morphology, set forth - - rather emphatically by 

 A. H. ('lark on the base of his theory, are meant as a tribute called forth 

 by my admiration for the eminent specialist in Crinoids, not as a wish 

 to refute his theory, which seems to me a superfluous task. Both the said 

 theories, besides bearing evidence of most unusual conceptions of mor- 

 phology, are at variance with the fundamental principle of phylogeny, 

 that evolution goes from the lower towards the higher organization, not 

 the inverse way (due allowance being made, of course, for the rarer cases 

 of regressive development, as e. g. the Acoela, which is, however, only an 

 apparent exception to the rule). 



This objection does, of course, not apply to the theory of Boas, that 

 the Echinoderms have developed from some fixed form of Coelenterates: 

 but otherwise this theory is, in my opinion, no more acceptable than are 

 those of A. II. Clark and Simroth. As stated above, I cannot enter on 

 a detailed discussion of the reasons given for this theory, but must con- 

 fine myself to making a few objections, which, however, would appear to 

 suffice for proving tin- unlenability of the theory. 



One of the main facts adduced by Boas as support for his theory is this 

 that in the Crinoids - and, mind well, not the more primitive Pelmalo- 

 zoa, the Cystids, the simpler forms of which, at least, do not show any 

 external signs of a radiate structure 6 ) the water-vascular system re- 



') I". A. Hal IHT. Kchinodcrma. in Kay Lankester's Treatise on /oology. Fart III. llion. 

 -) II. Bury. The metamorphosis of Echinoderms. Quart. .lourn. Micr. Sc. :iS. 189.Y p. 93. 

 'I A. H. Clark. A Monograph of Existing Crinoids. I. I". S. Nat. Mus. Bull. S2. I'.H.Y 

 4 ) .1. K. V. Boas. Xur AulTiissiinn diT YiTwandlschafts-Verhaltnisse der Tien-. I. 1!H7. 

 6 ) H. Simroth. Ober den Ursprung der Echlnodennen. Verb. d. Deutsdi. Zool. (Jes. ]\n 

 *) The radiate structure of Echinoderms is regarded as requiring their derivation from 

 "einer i'x<|iiisil radiar gebauten Abtcilung fi-stsit/.ender Tien-" (Op. cit. p. 'Jl i. 



