ECHINOIDEA. II. 



the use (or rejection) of generic nanies first nsed for fossil forms, since I retain the names Arhacinn. 

 Porocidaris and Stercocidaris. As regards Stcrcocidaris. I think it quite right to maintain that name, 

 the structure of the test being so characteristic that it seeins beyond doubt that the recent and fossil 

 species belong to the same genus. (Comp. Doderlein. Op. cit. p- 95.) Regarding Porocidaris. I find it 

 rather donbtful, indeed, whether it realh" belongs to the same genus as the fossil type, and perhaps 

 it would be better to create a new genus for it; for the present, hovvever, I will lea\c that undecided. 

 It was probabh' wrong to accept the name Arbaciiia — even if the species forbcsianus had not 

 proved to be a Prioiiccliiiius. On the other hånd, it was probably unnecessar)- to revive the name 

 Cænopcdiiia — but upon the whole I must maintain that in those families, where the pedicellariæ are of 

 great s\stematic importance, it is generally quite impossible to sav with certainty to which genus, 

 or in several cases even to which family, a species belongs of which only the test is known, as is 

 generalh- the case with the fossil forms. To my remark on this subject (Part I. p. 85) that identical 

 structure of the test is no proof of near relationship , Professor Agassiz objects (p. 107) that we are 

 perfectly justified in retorting that similarit}- of the pedicellariæ is no proof of relationship as shown 

 by the structure of the test, and we are not warranted in classifying together forms which agree onl\- 

 in the structure of the pedicellariæ, and differ in the structure of the test . I quite agree with this 

 and have never thought of niaintaining that the structm-al differences found in the tests of the differ- 

 ent forms were of no systematic valne, and I think that Agassiz will be unable to point out ans- 

 case of my having associated forms differing essentially in the structure of the test on account of their 

 pedicellariæ being alike in structui'e, except — perhaps — among the Cidarids, where my material did 

 not allow me to study sufficienth- the differences in the structure of the test. Professor Agassiz is 

 not at all entitled to say that I .recognize(s) only such affinities as are indicated b\- the structure of the 

 pedicellariæ. Affinities indicated by other structural features have little or no interest for him, or are 

 entirely erroneous. It will be a great saving hereafter if illustrations of Echini are limited, as he would 

 have us limit them, to figures of pedicellariæ«. — I need again only refer to the chapter on the classi- 

 fication of the Diadematids in m\- work on the Siam-Echinoidea for refutation of this assertion, and as 

 regards the illustrations a mere glance at my work will show that I have figured the species treated 

 there as carefully as possible. I wish Professor Agassiz had done so with all the species described by 

 him — that would have saved his fellow-workers a great deal of trouble; I ma\' remind the eminent 

 author of such species as Ecliinus W'allisi. Dorocidaris Bartlcffi. Hnniasier Me^itzi. On the other hånd, 

 I would maintain that for a preliniinary description of some species, figures of the pedicellariæ ma)" be 

 much more valuable than a figure of the whole animal, on which none of the more important char- 

 acters eau be seen. And it may also be suggested that not everybody perhaps can afford the e.xpense 

 of so copious illustration as that given in Professor Agassiz' last magnificent work. 



Against the results of my studies on the Echinotlmridæ Professor Agassiz has made a great 

 many objections, only very few of which, however, I can acknowledge as maintainable. I shall auswer 

 them one by one in the order in which they are set fortil. 



Firstly, Professor Agassiz objects to the arrangement of the figures of pedicellariæ in my piates; 

 he finds it almost impossible to compare the figures of pedicellariæ of the different species < without 

 a guide or key to their arrangement (p. 81). It is, indeed, rather a difficult questiou how to arrangc 



The Ingolf-Expedition. IV. z. 7 



