Introduction. 



vSitice the publication of the first I'art of tliis work (19031 three great and hiolUv important 

 works on Echinoids have been pid)iished, \ iz, I)e Meijere: Die Kcliinoidea (Kr Sibofra-Expedition 

 (1904. Siboofa-Expeditie. XLIIIl, A. Agassi/,: Tlie Panamic Deep-Sea Echini (1904. .Mtni. Mns. Conip. 

 Zool. XXXIl and L. Doderlein: Die Echinoiden der deutsclien Tiefsee-Ex])edition (ic)()6. Deutsche 

 Tiefsee-Exped. 1898—99. Kd. \"). De Meijere and Doderlein agree with nu- n])on the whole in tlie 

 \iews on the classification of the regular Echinoids and (in the systematic importance of pedicellarite 

 and spicules set forth by me in the first ])art of this work and in my work on the Kcliinoidea ili of 

 the Danish Expedition to Siam 1899— igoo (Mem. Acad. Roy. d. vSc. et d. Lettres de Danemark. 7. Ser. I. 

 1904). De Meijere only reserves his opinion as to ni\- clas.sificatiou of the Cidarids, though recognizing 

 the importance of the differences in the structure of the pedicellari;e made known bv me: his objec- 

 tions that ni\- diagnoses of the genera do not correspond with some of his new species and that mv 

 classification leads to a great dismemberment of the system, I ha\-e replied to in ni\ ])aper On some 

 Echinothnrids from Japan and the Indian Ocean (Ann. Nat. Hist. Ser. 7. Vol. Xl\'. i(p4. p. 91 — 92). 

 Doderlein after most careful and extensive researches states the general correctness of m\- views, 

 though, as might be expected from his somewhat better material, he has been able to impro\c the classi- 

 fication in se\-eral respects. Above all his results as regards the classification of the r/zA/^ivrAr arc highh 

 important, antl his arrangement of this family will doubtless prove correct, in an\- case for the ver\- 

 largest part of it; upon the whole, I think, Doderlein is quite right in the several corrections of ni\ 

 arrangement of genera and .species of the regular Echinoids, though on this occasion 1 cannot enter 

 on a further discussion thereof. (I must, lu)wever, reserve my opinion as to Doderlein's views of the 

 species of Sterrchiruis, till I ha\e made renewed studies on this group, which I intend to undertake 

 in the works on the Echinoidea of the Cierman and the Swedish .South Polar Expeditions). On this 

 occasion I can only express my admiration for the ver\' clear and sound wa\' in which Professor 

 Doderlein in his Introduction sets forth the signification of such structures as the jjedicellaria; in 

 the classification of Echinoids and meets the different olijections wliich have been or might be made 

 against this use of them. 



In marked contrast to these two authors Professor .\. Agassiz practicalh' rejects all \\\\ residts, 

 and expresses his contrary opinions in a wa\ that seems to me not justified e\en by .so great a renown 

 as his. The objections set forth b\ the famous author I do not find very strong, except as regards 

 the way in which they are expressed; but, of course, anv criticism by st) eminent an authority' on the 

 Echinoidea demands a careful and detailed consideration. It was m\- intention to publish a repl\ to 

 the more personal criticisms of Profes.sor Agassiz as a separate paper in some Periodical : but though 

 I might well be entitled to have published in some American Journal a defence against an unjust 



