14 DR. TH. MORTENSEN. 



scribed as Oj)hiopliiteus Henseni in the Echinodermenlarven der Plankton 

 Expedition (p. 62, PI. VII, 2). The occurrence of a similar — though quite 

 distinct — larva at the Bermudas is not at all against the supposition 

 that the larva figured by Kerr belongs to 0. nigra, since this genus is 

 also represented at the Bermudas (by the species Ophiocoma echinata 

 (Lmk.) and 0. pumila (Ltk.). 



This larva has also been observed at Port Erin by Dr. H. C. Chadwick, 

 who showed me on my visit there (at the end of July) figures he had made 

 of these and many other Echinoderm larvae. May we hope that he will 

 soon publish his many beautiful figures and interesting observations on 

 the Echinoderm larvae ? They would doubtless prove of great value to 

 students of these larvae, which are so interesting from both a morpho- 

 logical and a biological point of view. Even if the larvae can at present 

 only partly be referred to species, they are, at least most of them, so 

 well characterized that they can be recognized with certainty, and the 

 observations made on the larvae of hitherto unknown origin are by no 

 means lost, but may be directly transferred to the species to which 

 some such larvae are later on proved to belong. 



V — Spatangus purpureus. 



This species is one of the very first Echinoderms of which artificial 

 fertilization and rearing of the larvae were undertaken. It was A. Krohn 

 who did so in Messina in 1853 (" Uber die Larve von Spatangus pur- 

 pureus," Midi. Arch., 1853, p. 253, Taf. VII). He did not succeed in 

 rearing it to metamorphosis, but still so far that he thought he was 

 able to recognize it in free-swimming specimens. In another paper, 

 " Beobachtungen fiber Echinodermenlarven " {ibid., 1854, p. 208), he 

 gave them some further observations on the structure of this larva, from 

 which it appears that it is characterized especially by the postoral, 

 postero-dorsal, and posterior rods being fenestrated only in their outer 

 part, a considerable portion at their basis remaining unfenestrated ; 

 further the postero-lateral processes (" auricularfortsatze ") are "aus- 

 serst kurz, breit und abgerundet." In my Echinodermenlarven der Plank- 

 ton Expedition, as well as in Nordisches Plankton I have accordingly given 

 these characters for this larva, no later observations having been made 

 on it. The observations of Krohn are, however, not very detailed, and 

 especially it is an important objection that the reared larvae did not reach 

 a very advanced stage. There must be several other Spatangoid larvae 

 in the Mediterranean, and as their specific characters are not sufficiently 

 known we have no guarantee that the pelagic larvae which Krohn re- 



