34 DE. p. H. CAllPENTKli. OJ; CERTAIN POINTS 



closely similar to that o£ the youug Echiuid, and ou p. 89 he 

 said : — 



" II existe, eutre le systeme dorsoceutral des Asteriadees et celui des Eclai- 

 noidees, considere daus sa totalite et dans ses rapports aux autres systemes du 

 test, comme dans ses parties constituantes, ime similitude de structure et une 

 conformite de modifications qui achevent de faire concevoir tant I'unite de sou 

 plan morpbologique primitif, que la nature identique du jeu des organesqui y 

 apjDortent les alterations earacteristiques des unes et des autres." 



I do not know of any passage in Loven's writings which would 

 authorize the Sarasins in saying that he attempted to derive the 

 Echinids from the Crinoids. They are described in his work on 

 Fourtalesia * as the " joint-heirs " of some remote ancestral type ; 

 and the Sarasins seem to have altogether forgotten or to be un- 

 acquainted with the following remarks on p. 57 of the same 

 memoir : — 



" And so close is in reality, on either side, the general conformity in structure 

 of the geminous pores, as to cause the lineage of the Archseonomous Echinoidea 

 to gravitate forcibly towards that group of antique Cystoidea of the Silurian 

 era, different as these no doubt were in other respects, in the total absence — at 

 least in the adult — of a calyx, and in the distribution of the pores all over the 

 perisome." 



Eurther on, in the same work (p. 61;, Loven described his own 

 position as follows : — 



" Years ago it occurred to me, as it had to others, that the general resemblance 

 of the ' apical ' system in the Cidaridte, Saleniadce, and Echinidse to the calyx 

 of certain Crinoidea, might be a morphological fact of importance with regard 

 to a true perception of Ihe homologies of the skeletal constituents in the Echi- 

 noderms generally." 



And on the next page he says : — 



" It was at a very remote geological period that the classes of the Echinoderms 

 branched off from their ancestral trunk, at the same time inheriting in common 

 certain important characteristics, the actual presence of which still holds 

 together their diversified forms." 



Although differing from Loven as regards some of the particular 

 plates which are mutually homologous in the apical systems of 

 Crinoids and Urchins respectively, I hold as strongly as he does 

 that the apical system is fundamentally identical in structure in all 

 the Echinoderm classes in which it is represented. This has been 

 my position ever since I began to write on the subject in 1878 f. 



* Log. cit. p. 81. 



t " On the Oral and Apical Systems of the Echinoderms," Quart. Jouru. 

 Micr. Sci. 1878, vol. xviii. p. 351. 



