231 
(p. 46). He even maintains that the Cidarids have given rise to 
Diadematoids independently at different times, the recent Aspido- 
diadema being regarded as a ,,;neu erfolgte Abwandlung von Cida- 
riden" (p. 46). 
Tornquist's argument for deriving the Diadematoids from 
the Cidarids, viz. the simple ambulacra, is evidently quite insuf- 
ficient as basis for such a conclusion. I need only recall the fact 
that also the Lepidocentrids have simple ambulacra. Further, as 
regards the position of the pores, upon which Tornquist lays 
so much stress, it is anything but certain that the horizontal 
arrangement is the more primitive. In the young Cidarids the 
pores stand very obliquely, assuming in the course of development 
gradually a more horizontal position, as first shown by Dåderlein 
(Die Japanischen Seeigel. I. Cidaridae u. Saleniidae 1887. p. 30). 
The vertical position of the pores is also shown very clearly in the 
beautiful figures of a young "Goniocidaris" (Austrocidaris) canali- 
culata given by Lovén in his ”Echinologica” Pl, II; in my ""Siam- 
Echinoidea” I. p. 8 I have mentioned the same feature for the 
Young f Stephanocidaris" (Plococidaris) bispinosa. Of no less im- 
portance is the fact that also in Bothriocidaris the pores are 
vertically placed. Jackson (p. 57) has no doubt that the super- 
posed position of the pores is the primitive, and I must fully join 
him in this view, both the embryological and palæontological 
evidences being decidedly in favour of it. — Finally as regards 
Tornquist's suggestion that Aspidodiadema represents a separate, 
recent offshoot from the Cidarids, this is evidently the result of 
disregarding all other characters than those afforded by the coronal 
plates. I see, however, no reason to enter more particularly upon 
this question here. 
Bather's .reason for rejecting the derivation of the Diadema- 
toids from the Lepidocentrids, that the primary interambulacral 
plate has disappeåred in the former, does not seem. to me better 
than that adduced by Tornquist. . It appears that Dr. Bather 
has not taken the Echinothurids into consideration. Here we see 
