606 SUMMARY OF CURRENT RESEARCHES RELATING TO 



and that more especially at first sight, to present a combination of 

 characters." Only one new Ophiurid — Ophioscolex Cojypingeri, and one 

 new Astrophytid^J.. Lymani — are described. Specimens were ob- 

 tained of that Cuvieria antarctica which has so striking a resemblance 

 to the Psoitis pJiantajms (G. Fabricn) of the Arctic Seas. A new 

 species of Strongylocentrotus {S. hullatus) of large size is described, 

 and an account is given in full of a smaller form, which, the author 

 says, he was for long inclined to regard as another species ; but a 

 " long and close study of other members of the genus has convinced 

 me that the form of the arc of pores may vary very considerably 

 during growth." 



Nervous System of the Ophiuroidea.* — M. N. Apostolides points 

 out that the perineural space in which the nerve-ring is situated forms 

 a circular canal, which is bounded by the wall of the second discoid 

 ossicle, and by two membranes which, starting from the point where 

 the oesophagus passes into the stomach, extend above and below it, and 

 become connected with the ossicle just mentioned. In this space the 

 nerve-ring is set vertically while its rays are horizontal. The water- 

 vascular ring lies outside the nerve-ring, and, as its branches pass out 

 by the same orifices as the nervous rays, it follows that there is always 

 a very close connection between the two sets. Where the nerve and 

 the ambulacral vessel are folded back, the perineural cavity communi- 

 cates with the other spaces of the body. This explains how Teuscher's 

 injection made its way around the nervous system. Histologically the 

 nervous band consists of two very distinct tissues, one composed of a 

 mass of cells of a brown colour and with large nuclei. These cells 

 are comparable to the pigment-cells of the Vertebrata. The rest of 

 the band consists of extremely fine fibres, among which a high magni- 

 fication reveals the presence of bipolar cells ; this is the only part of 

 the band which is really nervous ; it only, however, constitutes a 

 small portion of the whole. There are no special ganglionic enlarge- 

 ments on it, and when a swelling is developed, it is at the expense of 

 the non-nervous portion. The nerve-rays give off^ on each side two 

 branches, the superior of which is directed towards the first tentacle. 

 When it has got near this it bifurcates ; the two branches of the bifur- 

 cation surround the end of the tentacle, and then they anastomose with 

 the opposite side, so as to form a complete circle. No distinct nerve- 

 branches could be made out on the wall of the tentacle. The 

 lower branches are directed to the muscles between the angles of the 

 mouth. 



Viviparous Chirodota.f — Professor H. Ludwig has published his 

 promised essay on this interesting Brazilian form. The single adult 

 was 18 mm. long and 4*5 mm. thick, cylindrical in form, and rounded 

 off at either end. The surface is covered, except along the rays, by 

 opaque tubercles, in each of which were found more than one hundred 

 of the characteristic " wheel-organs " of the genus ; and, in addition to 

 these, there were, in smaller number, calcareous rods thickened at 



♦ Comptes Rendus, xcii. (1881) pp. 1424-6. 

 t Arch, de Biol., ii. (1881) pp. 41-58 (1 pi.). 



