109 



By this time I had to leave Misaki, so that there was no opportunity 

 of rearing the larvae beyond the first stage. This species being the first 

 deep-water Echinoderm, the development of which has been studied - 

 all other Echinoderms hitherto used for developmental studies being 

 mainly littoral - - this case is very interesting, as it proves that at least 

 some deep-water Echinoderms may have typical pelagic larvae. (The 

 species is known to have a bathymetric range of ca. 100 800 meters). 



The shape of the larvse (PI. 

 XIV, Fig. 1) does not present 

 any unusual features; it is, 

 however, not old enough lo 

 show whether it will offer any 

 marked special features in ils 

 full shape. No pigment was 

 present at this stage. 



The skeleton (Fig. 45) is in 

 conformity with that of other 

 Clypeastroid larvae, the body 

 skeleton forming a basket struc- 

 ture; there is as yet no large 

 fenestrated plate developed in 

 the posterior end of the body, 

 which would seem to indicate 

 that such is not formed in this 

 larva, since in other larvae it is found to develop already in the quite 

 young stage. The body rod is strongly thorny, the recurrent rod smooth. 

 The upper ventral transverse rod is well developed, smooth; there is no 

 indication of a lower ventral transverse rod. The postoral rods are fenes- 

 trated, strongly thorny; the anterolateral rods are also rather strongly 

 thorny. 



Peronella Lesueuri (Val.). 



Pis. XV XVI. 



In my paper ''On the development of some Japanese Echinoderms" 

 1914 I gave a short summary of the development of this species under 

 the name of Laganum decagonal?; the wrong identification was due to lack 

 of litterature. In the following year Grace Medes published a paper on 

 "The Pluteus of Laganum sp." 1 ), the identification of the species being 

 omitted. As the larva described in that paper was very much like that 

 of the Japanese species, I was, of course, very anxious to learn to which 



') Papers from the Department of Marine Biology of the Carnegie Inst. Washington. 

 Vol. VIII. 1915. 



Fig. 45. Skeleton of the larva of Laganum diplopora. 

 From the ventral side. 300 / 1 . Letters as in Fig. 20. 



