422 NATURAL SCIENCE. j UNE , 



opinions were given ; and this might have been rendered possible 

 by the insertion of a name here and there between brackets. For 

 instance, in chapter xx., on Regeneration and Asexual Reproduction, 

 it is stated that " In Ophiurids regeneration of the whole body from 

 one arm never occurs." Has Dr. Lang considered Semon's case of 

 Ophiopsila aranea [Jena. Zeitschr., xxix., p. 585), and has he rejected it ? 

 We cannot tell. In the same chapter it is doubted whether " Division 

 of the body into two nearly equal halves with subsequent regenera- 

 tion " has been observed in Holothurians. Does Dr. Lang doubt the 

 observations of Chadwick (see Natural Science, vol. v., p. 4), or is 

 he ignorant of them ? We cannot tell. Was the cautious paragraph 

 on autotomy in crinoids written before or after Dr. Lang had read the 

 interesting account given by Danielssen and quoted in Natural 

 Science (vol. v., p. 5) ? We cannot tell. 



In his account of the development of Antedon, Dr. Lang has 

 followed Seeliger throughout, as the student may for this once gather 

 from the figures. I am glad to find him criticising the expression 

 " Cystid stage," in so far as it implies any recapitulation or morpho- 

 logical affinity ; but I must protest against his falling into a precisely 

 similar error in his next section. He says, with all the emphasis of 

 spaced type, that in the pentacrinoid stage " the correspondence of the 

 attached and stalked larva of Antedon with the Inadunata, especially 

 with the so-called Larviformia, is quite remarkable, immediately 

 striking the eye." With equal emphasis I deny that any except a 

 superficial resemblance exists. The stem is totally different : the 

 base is, we know, dicyclic ; in nearly all so-called Larviformia it is 

 monocyclic : the radials and basals are quite regular ; in most Larvi- 

 formia they are more or less irregular, owing to the bisection of some 

 radials : the arms are branched ; in the Larviformia they are single : 

 the temporary anal plate, though no doubt homologous with that 

 occurring in some Larviformia, is not comparable in situation or course 

 of development. In short, Professor Lang's emphatic dictum is a 

 typical example of those rash and inexact comparisons that drew so 

 just and vigorous a protest from Professor von Zittel in his address 

 to the Geological Congress (Natural Science, vol. vi., p. 308). 



Adequately to discuss the chapter on Phylogeny would require a 

 special article, though it deals only with the origin of the Echino- 

 derma and the relations of the classes. A primitive bilateral form, 

 corresponding to the Dipleurula larva, is sketched out. Since radiate 

 structure is a consequence of an attached mode of life, " all echino- 

 derms must once have been attached animals." Attachment took 

 place by the anterior end of the body (larval organ, prag-oral lobe). 

 " The body then developed chiefly in the region of the mouth and 

 tentacles. The hind part with the anus was at first a lateral projec- 

 tion, which gradually subsided and less and less disturbed the 

 radiate arrangement. On this view the greater extension of the anal 

 interradius, found especially in palaeozoic crinoids, may possibly be 

 an original condition, with which is connected the occurrence of 

 special anal plates in that interradius." Here, again, the facts of 

 phylogenetic development, as deduced from actual fossils and not 

 from imaginary archetypes, force me to join issue with Dr. Lang. 

 Granting the lateral position of the anus, the evidence, at all events 

 of the Inadunata, shows that the widening of the anal interradius and 

 intercalation of anal plates was a secondary condition, of which the 

 initial rise can be traced just as easily as its final decline. 



This attached stage has been persisted in by the Crinoidea, 

 although many genera have, at different periods, relinquished it for a 



