ECHINOIDEA. II. 



21 



cellarise; they are certainly very peculiar, but may be embryonic conditions of unknown pedicellariae 

 similar to those he figures for Ph.placenta. As for his remarks on Phormosoma tenue, I would suggest 

 to Dr. Mortensen that the Report on the Challenger -Echini was issued in 1881, and that his memoir 

 was published in 1903; he can scarcely expect genera proposed in 1903 to have received any recogni- 

 tion in 1881 . 



It is possible that the genus Hapalosoma (not Hoplosoma) cannot be maintained, in which case 

 the only species, pellucidum, would have to be referred to the genus Arceosoma, since its peculiar glo- 

 biferous pedicellariae are evidently only a special development of the tetradactylous pedicellariae of 

 the latter genus, as shown by Dr. de Meijere. That they are not embryonic conditions of unknown 

 pedicellariae is certain; otherwise, fully developed forms would also have been found among the not 

 very few specimens seen by me, and Dr. de Meijere especially would have found them in the very 

 rich material he has had for study. Whether now the genus Hapalosoma has to be maintained (as I 

 think it has| or not, I certainly did not deny the close affinity of A. pellucidum with A. coriaceum 

 and tesselatum because I suggested a separate genus for the former, but, on the contrary, I suggested 

 a new genus for it, because I found it too distantly related to A. coriaceum and tesselatum to refer 

 it to the same genus with these species. The use of the word because in this place is thus not quite 

 fair, and the same holds good in other instances, thus for example when it is said on the same page 

 as the above: I have nothing to say regarding Dr. Mortensen's sneers at descriptions of pedicellariae, 

 because they do not fit with his classification . My criticism of the description of the pedicellariae of 

 Phormosoma tenue (as well as of other species) given by Professor Agassiz is certainlv sufficiently 

 justified by the character of that description, as will be agreed, I imagine, by anybody who will take 

 the trouble to read my remarks on that subject (Part I. p. 57). 



That Professor Agassiz could not in 1881 recognize the genera proposed by me in 1903 is 

 self-evident. But, nevertheless, I think the remark to which Agassiz refers here quite justified 

 1 Part I. p. 55). After quoting from the Challenger -Echini p. 87 as follows: In the only species of 

 the group of which the Challenger collected a complete series (Phormosoma tenue) there was little 

 difficulty in recognizing the young as belonging to the adult I continue: We could scarcelv wish 

 to find a more pregnant proof of the difficulty or impossibility of determining Echinids without taking 

 the pedicellariae .into consideration . . . With regard to the excellent long series of Phormosoma tenue. 

 there are among the specimens referred to this species by Agassiz at all events two different genera, 

 but no genuine Phormosoma /» Professor Agassiz has now established a new species of the genus 

 Kamptosoma, A", indistinctum A. Ag., on a specimen from the Challenger St. 272, referred to Phor- 

 mosoma tenue (p. no). I venture to imagine that a more careful examination might have made it 

 possible to recognize this specimen as belonging to a separate genus already even in 1881 ; of course, 

 it would at that time have been impossible to know the name to be proposed by me later on, but 

 the genus really did exist already at that time. It is also worth noticing that this genus is sufficiently 

 characterized by its peculiar ambulacral structure alone, without regarding the pedicellariae and spines. 



Professor Agassiz does not deny himself the pleasure of correcting me when mentioning 



Phormosoma^ aster/as as the last of the Echinothurids described from the Challenger, (p. 86); lam 



sorry to have to call his attention to the fact that, since I had already treated all the other species, 



