ECHINOIDEA. II. 



19 



That I signore all thai has been saitl of the different species of ICchiiiothurice relating to 

 the actinal and abactinal systems and the spines, because I (he) think(s) the Echinothurida; are not 

 adapted for examination in the dry state» needs no sjjecial refutation. I have found no reason to 

 repeat all the facts made known b\- the different authors on Echinothuridce, as in general I do not 

 think it necessar\- to repeat all that has prexiously been nuide known each time some additional 

 information is given. But 1 am sure that I have not ignored what was iDrevioush' known of the 

 Echinotfmridcr when giving the new classification resulting from my predecessors' and m\- own re- 

 searches. That the Echinothuridse are not adapted for examination in the dr\- state 1 have not said. 

 On the contrar\' I have said -that the arrangement of the plates is generalU' onl\- to be seen in dried 

 specimens . I!ut , I continue the Echinothurids are only ver>- little adapted for preservation in 

 dried state, and if the material in hand be slight one does not like to destroy it for the sake of 

 determination; (p. 43). This remark seems to me incontestable. 



I do not at all claim to give a perfect classifications of the Echinotliitridcr. On the contrar\- 

 I have said (p. 65): As has been done above in the Cidarids I shall also here expressly state that I 

 do not regard the generic diagnoses given here as complete. As well the structure of the test as the 

 inner anatom>' stands in need of an exact examination in several of the genera. I must, however, 

 regard all tlie genera established here as good ones, and also the limitation of the old genera Phornio- 

 soma Sind Asthenosotna is no doubt correct. Only the genera Arceosoma and Hygrosoma are perhaps still 



taken in too wide a sense That the new genera established by me are < based wholly upon the 



structure of the triphyllous and tridentate pedicellarias is in so striking contest with the statement 

 given b^■ Professor Agassiz himself a few lines above that my classification is based first upon the 



characters of the spines, as if his predecessors had not mentioned them in any wa\- ; next upon 



pedicellarise, tube feet, pores and spicules , that I need say no more about it. That m\- predecessors 

 have both mentioned and described the spines more or less accurately, I have never denied or thought 

 of concealing; but it is one thing to describe them, another to use them properly for systematic pur- 

 poses, and I do not see that Professor Agassiz has made such use of the spines. Even now, 

 after ni}- pointing out the importance of the differences found in the structure of the primary actinal 

 spines (ending in a thick fleshy sack in Phorinosoiiia, in a curious white, naked hoof in the other 

 genera — Kamptosoma still remaining unknown in this respect), he does not recognize this fact, though 

 without giving any reason for not doing so, onl}- referring to a statement in the Challenger;;-Echi- 

 noidea (p. loi): -The presence of sheathed spines in two species of Phorniosovia shows thai this cha- 

 racter, which at first seems to separate so strikingly from the rest of the group Asthenosoma grubii, 

 is evidenth- one of little value, and which may be more or less developed in specimens of the same 

 species in the same state of growth . To this statement I remarked (Part I. p. 48): the facts here put 

 together by Agassiz are quite different: in A. grubci it is the spines on the abactinal side that are 

 wrapped b>- a bag of skin, and the spine itself is of the common structure, a perforate tube ending 

 in a fine point; in Ph. placnita and the species allied to it, it is the primary spines on the actinal 

 side that are clavatel)- widened in the point and wrapped by a thick bag of skin. These spines must, 

 of course, be compared with the primar)- spines on the actinal side of the other species, but then wc 

 find a marked difference, these spines of the other species not being covered with skin — as far as is 

 known — but ending- in a larger or smaller hoof, distincth' marked off from the spine itself . Pro- 



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