ECHINOIDEA. II. ig 



That I cigiiore all that has beeu said of the different species of Echiiiothuriæ relating; to 

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

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

 repeat all the facts made known by the different anth.ors on Ecliinotlmridæ, as in general I do not 

 think it necessary to repeat all that has pre\iously been made known each time some additional 

 information is given. But I am sure that I have not ignored what was previonsl}- known of the 

 Echinofhuridcc when giving the new classification resnlting from m\' predecessors' and mv own re- 

 searches. That the Echinothuridæ are not adapted for examination in the dr\' state I have not said. 

 On the contrary I have said that the arrangement of the piates is generally onl}- to be seen in dricd 

 •specimens . «But , I continue the Echinothufids are only very little adapted for preser vation in 

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

 determination (p. 43I. This remark seems to me incontestable. 



I do not at all claim to give a perfect classification of the Echinothuridæ. 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 gi\en here as complete. As well the structure of the test as the 

 inner anatomy stands in need of an exact examination in se\eral of the genera. I must, however, 

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

 sonia and As f/ienoso/ua is no doubt correct. Only the genera Aræosoma and Hygrosoiiia are perhaps still 



taken in too wide a sense That the new genera established by me are ^based wholh- upon the 



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

 given by 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 way ; next upon 



pedicellariæ, 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 tise them properly for systematic pur- 

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

 after my pointing out the importance of the differences found in the structure of the primary actinal 

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

 genera — Kaiiipfosovia still remaining unknown in this respect), he does not recognize this faet, though 

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

 noidea (p. loi): cThe presence of sheathed spines in two species of J'hormosovia shows that 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 liere put 

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

 wrapped by a bag of skin, and the spine itself is of the conimon structure, a perforate tube ending 

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

 side that are clavateh- widened in the point and wrapped b)- a thick bag of skin. These spines nnist, 

 of course, be compared with the primary spines on the actinal side of the other species, but then we 

 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, distinctly marked off from the spine itself . Pro- 



