ECHINOIDEA. I. 



cellariæ of the Echinoids give good specific characters. Stewart, Koehler, Doderlein, Wyv. 

 Thomson, a. o., but especially Per ri er and Agassiz have later described pedicellariæ of a great 

 many different Ecliinoids, and have shown that here an immense richness in forms is fonnd, and that 

 they give characters with regard as well to families, as to genera and species. Nevertheless the pedi- 

 cellariæ have only a few times (in Wyv. Thomson's classical work on the Porcupine»-Echinoids 

 (395) ^^^'^ Doderleins as excellent work on the Cidarids (116)) been treated as being of importance in 

 the systematic works; generally they have only been mentioned as a matter of small importance beside 

 the description proper, and often no attention at all has been paid to them. Rarely all the different 

 forms of pedicellariæ in a species are described, and still less in all species of the same genus; of one 

 species an oi^hicephalous and a tridentate pedicellaria is figured, of another a valve of a globiferous one, 

 of a third perhaps none at all, etc. In this way, of course, we shall never get a clear understanding 

 of the systematic characters which may be found in these small organs. The pedicellariæ in 

 effect give absolutely excellent systematic characters, sometimes only specific characters, 

 sometimes also generic ones. 



The use of the pedicellariæ in classification is attended with great advan tages; they do not 

 change their form with age, but are in the newly metaraorphosed Echinoid of the same form as in 

 the grown one, only somewhat smaller in the small specimens. It is therefore (oftenest) possible, by 

 means of the pedicellariæ, easily to determine quite small Echinoids with absolute certainty — at 

 all events as to genus. Another advantage is that it is not necessary to remove the spines in order 

 to get a view of the tubercles, the specimens have not to be destroyed for the sake of determination. 



It may, perhaps, seem unreasonable to lay so much stress, as is done here, on so minute fea- 

 tures as the pedicellariæ — to use them for the characterizing of as well species as genera and 

 families. But when it proves to be a real faet that these minute features give excellent, constant 

 characters, it may be taken to be reasonable to use them without regard to their being small or 

 large. Surely any student of Echinoids will also feel it as a great advantage not to be obliged to be 

 contented with all tliese relativities, as the length and number of the spines, the size of the 

 tubercles, the form of the test etc. To all these things, of course, regard must always be paid, and 

 so has also been done here, as far as the material has permitted. But the pedicellariæ are, at least, 

 as important. I can completely subscribe the expre.s.sions of Stewart (381 p. 912): It seems to me 

 most desirable that minute, and even apparently trivial, features should be given in the descriptions of 

 species, and that when this is more done, we may find affinities between forms, we should otherwise 

 not suspect, and be enabled by the examination of even an ambulacral tube or pedicellaria etc. to 

 determine a species without the denudation of portions of the coroua, which is sometimes not 



desirable». 



The supposition by Stewart that by an examination of the pedicellariæ etc. we might find a 

 closer relation between forms not otherwise regarded as related, has been amply justified by these 

 researches, even to so high a degree that the classification hitherto used proves to be quite a 

 failure (with regard to the groups treated of here). A good proof of the correctness of the new classi- 

 fication given here, which has been found especially by the examination of the pedicellariæ, is found 

 in the faet that forms with the same kind of pedicellariæ also agree in other important respects. To 



