ECHINOIDKA. II. IO , 



That I ignore all that has been said of the different species of Eehinothnrise relating to 

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

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

 repeat all the facts made known by the different authors on Echinothurida, as in general I do not 

 think it necessary to repeat all that has previously been made known each time some additional 

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

 Echiiiothtiridcc when giving the new classification resulting from my predecessors' and my own re- 

 searches. That the Echinothuridse are not adapted for examination in the dry state I have not said. 

 ( in the contrary I have said that the arrangement of the plates is generally only to be seen in dried 

 specimens . But , I continue the Echinothurids are only very 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 classification of the EchinothuridcB. On the contrary 

 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 anatomy stands in need of an exact examination in several of the genera. I must, however, 

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

 soma and Asthenosoma 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 trideutate pedicellarise -> 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 



pedicellarise, tube feet, pores and spicules , that I need say no more about it. That my 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 my pointing out the importance of the differences found in the structure of the primary actinal 

 spines (ending in a thick fleshy sack in Pliorniosoina, 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, only referring to a statement in the Challenger -Echi- 

 noidea (p. 101): The presence of sheathed spines in two species of Phormosoma shows that this cha- 

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

 is evidently 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. grubei it is the spines on the abactinal side that are 

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

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

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

 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- 

 s' 



