54 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Echinoderma. 



Hermaphrodite Holothurian.* — Hjalmar Theel describes the herma- 

 phroditism of Mesothuria intestinalis. The genital tubules, developed 

 on the " genital basis " from in front backwards, occur in male and 

 female sets. In the " genital strand," which is the foundation from 

 which the genital basis and the transitory genital tubules arise, there 

 are young germ-cells. The older genital tubules with unused ova and 

 sperms degenerate and show much phagocytosis. Ludwig notes in a 

 report on Theel's paper that hermaphroditism also occurs in Cucumaria 

 crocea, C. Isevigata, and Pseudopsolus macquariensis. 



Physiology of Echinoderms.f — Prof. L. Cuenot has made a series 

 of observations on certain points connected with the physiology of 

 Asteroids. He finds that the amo3bocytes multiply only by direct 

 division ; there is no organ having for its function the production of 

 amoebocytes. The digested food is absorbed by a system of lacunas, 

 lying on the radial casca, which communicate with the ovoid gland. In 

 Asterias ruhens, two longitudinal lacunas lie on each of the ten radial 

 casca. All these lacunas unite together, and pass ultimately into the 

 ovoid gland (plexiform organ) ; their contents probably there undergo 

 some change, and then pass by the nutritive lacunas to the oral and 

 aboral surfaces, where they probably reach the organs by means of 

 osmosis through the walls of the lacunas. In starfish and sea-urchins, 

 two kinds of excretory cells exist, tlie indigo-nephrocytes, represented 

 by the epithelium of parts of the digestive tube, and the carminate- 

 nephrocytes, represented by the epithelium of the coelom, of the peri- 

 lacunar and ambulacral cavities, and of Tiedemann's bodies, and by the 

 free amoebocytes and the internal cells of the ovoid gland. It is pro- 

 bable that the excretory substances produced by the cells excreting 

 carminate of ammonia fall into the coelom, and are taken up by the 

 phagocytes ; as already observed by Durham, the phagocytes are capable 

 of leaving the body by means of the skin-gills, whose walls they cross. 



Coelentera. 



Regeneration and Regulation in Renilla4 — H. B. Torrey finds 

 that colonies of Henilla readily regenerate lost parts. They exhibit a 

 strong polarity ; when a peduncle is removed by a transverse cut an 

 axial polyp is never regenerated in iis place, and vice versa. There is 

 an anterior limit beyond which anterior pieces do not regenerate pos- 

 teriorly, and a posterior limit beyond which posterior pieces do not 

 regenerate anteriorly. These correspond to the limits of the budding 

 zone. The colonies regulate themselves in a plastic fashion when cut 

 in certain ways, obliquely, for instance. It is thus possible to obtain 

 two new colonies, one of which retains the original peduncle with a 

 lateral polyp displaced into the position formerly occupied by the axial 

 polyp. Whether the colony develops symmetrically around this new 

 axis is not known. If the oblique cut makes with the colonial axis an 



* Bib. Svensk. Vet.-Ak. Handl., Bd. 27, Afd. iv. No. 6 (1901) 38 pp., 2 pis., and 

 12 figs. See Zool. Centralbl., viii. (1901) pp. 717-8. 

 t Arch. Zool. Exper., ix. (1901) pp. 233-59 (1 pi.), 

 j Biol. Bull., ii. (1901) pp. 355-6. 



