590 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Effects of Light on Eye of Prorhyncus.* — W. A. Kepner and 

 A. M. Foshee have investigated the effects of light and darkness on the 

 eye of Prorhyncus applaatus Kennel. They tind that stimulation by 

 light results in a contraction of the accessory or pigment cell. In 

 sustained darkness the cytoplasmic lamellae of the pigment cell open up 

 or move apart, and this results in the expansion of the cell. The three 

 cytoplasmic regions of the retinula or visual cell show more or less 

 marked changes in response to light and darkness. The nucleus- 

 bearing part of the visual cells widened somewhat in the dark. The 

 refractive middle segment (analogous to an ellipsoid of a vertebrate 

 retinula) disappears in continuous illumination, and is most conspicuoiis 

 in eyes that have been subjected to optimum illumination. The 

 rhabdome in light-adapted eyes is a rounded cone-shaped body, while in 

 those adapted to darkness it is an elongated trough-shaped structure 

 with its long dimension directed parallel to the axis of the animal. 

 Notwithstanding the analogy apparent between the structure of the 

 retinula of a vertebrate and that of Prorhyncus, there is no analogy 

 in functional changes. In the former it is the myoid that most 

 markedly changes form ; in the latter it is the rhabdome that is most 

 conspicuously modified in response to light and darkness. 



Erratum. — In the October number of the Journal, p. 469, it was stated that 

 Tylocephalum marsupium sp. n. had been obtained by Dr. Edwin Linton from 

 Bhinoptera bonasus ; it should have read " from Aetobatis narinari." From 

 Rhinoptera bonasus Linton obtained in 1887 Tylocephalum pingue, the type of the 

 genus. 



Incertse Sedis. 



Study of Phoronidea.t — Alexander Meek discusses the distribution 

 of Phoronis ovalis on the east coast of Britain, where it is the only 

 species known, and the strong probability that its larva is Actinotrocha 

 hranchiata — the only larval form known from that area. He calls 

 attention to the variability of the characters both larval and adult. A 

 survey is made of the species Phoronis ovalis Strethill Wright, 

 P. euxinicola de Selys Longchamps, P. architecta Andrews, P. busJcii 

 M'Intosh, and so on, and of the species of Actinotrocha. A brief 

 account is given of the development and metamorphosis. The afBnilies 

 are also discussed. According to the author Phoronis must be placed 

 amongst the groups of Invertebrates which present a stomodeul blastopore: 

 its metasome is directly homologous with the foot of Molluscs and with 

 the part of the body of Gephyrea which intervenes between the mouth 

 and the anus, the outgrowth which gives rise to the greater part of the 

 body of the adult. 



Bryozoa. 



Cyclostomatous Bryozoa of Japan.:}: — Yaichiro Okada deals with 

 seven genera and thirty-two species, including the following new 

 forms: — Crista simplex, Crisulipora ijimai, TubuUpora misakiensis, 

 T. radiata, Berenicea ampidliformis, B. rotunda and Lichenopora 

 sagamiensis. 



* Journ. Exper. Zool., xxiii. (1917) pp. 519-32 (1 pi. and 3 figs.), 

 t Eeport Dove Marine Laboratory, vi. (1917) pp. 33-48 (3 figs.). 

 X Annot. Zool. Japon, ix. (1917) pp. 335-60. 



