174 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Echinoderma. 



Notes on North American Starfishes.* — A. E. Verrill calls attention 

 to some apparent hybrids, e.g., between Asterias epichlora and Pisaster 

 ochraceus. He also discusses multiplicity of rays, which is common on 

 the north-west coast. Twelve of the forty north-west American species 

 of Asterias and Pisaster have normally six rays. A number of interest- 

 ing abnormalities are recorded, e.g., four-rayed forms of Ctenodiscm 

 crispatus. The advantages of having numerous rays, e.g., for holding the 

 food securely and holding to the rocks, are discussed. 



Regeneration in Ophiocoma pumila.f — S. Morgulis finds that if the 

 radial nerve is injured before cutting off the arm, only a small stump is 

 regenerated. If the nerve is destroyed near the disc, so little new tissue 

 is formed that it is difficult to recognise it at all. "Where the radial 

 nerve is left intact, a long new part is regenerated. In cases where the 

 brittle star throws off the arm at the place of injury to the nerve, there 

 is absolutely no regeneration from the cut surface thus produced, while 

 other arms in the same specimen with the nerve intact regenerate 

 normally. 



Ophiurans of San Diego. J — J. P. McClendon reports on a collection 

 from this region, which includes some new species — of Ophiomusium, 

 Ophiura, Ophiopholis, etc. "Although most of the species react 

 negatively to light, and hide under rocks and in sea-weed, sponges, etc., 

 some of them appear to protectively coloured." 



Mode of Feeding in Echinocardium and Spatangus.§ — H. A. G. 

 Horny old finds that the buccal tube-feet are extended, feel about in the 

 sand, broaden out terminally, seize a particle, and pass it to the spines of 

 the lower lip. These with the assistance of the upper-lip spines pass 

 the particles into the mouth. There is no shovelling of sand into the 

 mouth by ploughing through it. Robertson of Millport described the 

 action of the tube-feet and spines, and the author corrobates his 

 observations in great part. 



Development of Holothuria floridana.|| — C. L. Edwards describes 

 in particular the development of the tentacles, pedicels, and papillae. 

 There is no free Auricularia larva, but the embryonic stages are passed 

 within the vitelline membrane during the first five days after the 

 fertilisation of the egg. On the sixth day the embryo hatches as a larva 

 with five primary tentacles, four developed (projecting) and one as a 

 bud (buried in the skin), and also with one posterior pedicel. The order 

 of appearance in subsequent stages is carefully chronicled. 



Echinoderms of ' Thetis ' Collection. f — H. L. Clark reports on a 

 collection of fifty-four species collected by the ' Thetis ' from Lord 



* Anier. Nat., xliii. (1909) pp. 542-55 (7 figs.), 

 t Proc. Amer. Acad. Arts Sci., xliv. (1909) pp. 655-9 (1 fig.). 

 X Univ. California Publications (Zoology) vi. (1909) pp. 33-64 (6 pis.). 

 § Biol. Centralbl., xxix. (1909) pp. 759-62. 

 || Journ. Morphol., xx. (1909) pp. 212-30 (3 pis.). 



^ Sci. Results Trawling Expedition H.M.O.S. ' Thetis.' Australian Museum, 

 Sydney, Memoir iv. (1909) pp. 518-64 (12 pis.). 



