Introduction. 



Since tlie publicatioii of the first Part of tliis work (19031 three great and hijj^lily impoitaiit 

 works OU Echinoids have beeii published, viz. De Meijere: Die Echinoidea der Siboga-Expeditiou 

 (1904. Siboga-Expeditie. XLIII), A. Agassiz: Tlie Paiianiic Deep-Sea Echini (1904. Mern. Mus. Comp. 

 Zool. XXXIl and L. Doderlein: Die Echinoiden der deutschen Tiefsee-Expedition (1906. Deutsche 

 Tiefsee-Exped. icSgS-gg. Bd. \'). De Meijere aud Doderlein agree with me upon the whole in the 

 views on the classificatiou of the regular Echinoids aud on tlie s\ stematic importance of pedicellariæ 

 and spicules set forth by nie iu the first part of this work aud iu ui\ work on the Echinoidea |I) of 

 the Danish Expedition to .Siaui 1899—1900 |Méni. Acad. Roy. d. Se. et d. Lettres de Danemark. 7. vSér. I. 

 1904). De ]\Ieijere oul\ reserves his opinion as to my classificatiou of the Cidarids, though recognizing 

 the importance of the differences iu the structure of the pedicellariæ made kuown b\ me; liis objec- 

 tious that ui\ diagnoses of the genera do not corres])oud with some of his new species aud that uiy 

 classificatiou leads to a great dismembermeut of the system, I have replied to iu my paper ()u some 

 Echinothurids from Japan and the Indiau Ocean (Ann. Nat. Hist. Ser. 7. Vol. XIV. 1904. p. 91 — 92). 

 Doderlein af ter most carefui aud extensive researches states the general correctness of my views, 

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

 fication in several respects. Above all his results as regards the classificatiou of the Cidarida- aie highly 

 important, and his arrangement of this famih- will donbtless prove correct, iu au\- case for the \-er\- 

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

 arrangement of genera aud species of the regular Echinoids, though on this occasiou I caunot enter 

 OU a further discussion thereof. (I must, howe\er, reserve my opinion as to Doderlein 's views of the 

 species of Sterrchiniis, till I have made reuewed studies on this gronp, which I iuteud to uudertake 

 iu the works ou the Echinoidea of the (Terman and the Swedish vSoutli Polar Expeditious). ( )u this 

 occasion I eau ouly express m\- admiration for the very clear and sound wa\- iu which Professor 

 Doderlein iu his Introduction .sets forth the siguificatiou of such stvnctures as the pedicellariæ in 

 the classificatiou of Echinoids and meets the different objectious which have been or might be made 

 against this use of theui. 



In marked contrast to the.se two authors Profes.sor A. Agassiz practically rejects all m\ results, 

 and expresses his coutrary opinions iu a way that seems to me not justified even by so great a reuowu 

 as his. The objectious set forth b\- the famous autlior I do not find very stroug, except as regards 

 the wa\ in which the\ are expressed; but, of course, any criticism i)\ so eminent au authority ou the 

 Echinoidea demands a carefui aud detailed con.sideration. It was m\ intention to publish a repl\ to 

 the more personal criticisms of Professor Agassiz as a separate paper iu some Periodical ; but though 

 I might well be entitled to have publLshed in some American Journal a defeuce against au nnjust 



