68 SUMMARY OF CURRENT RESEARCHES RELATING TO 



recommends the mastery of tlie details furnislied by Barrois on their 

 development, and a study of mounted or living specimens of Carhasea for 

 the Cbeilostomata, of Zoohotryon jjellucidus for the Ctenostomata, and Crista 

 foUacea for the Cyclostomata. After a tabular list of families and an 

 index of names, the author enters on the systematic arrangement of the 

 genera and species ; the synonymy is here given, and there is an elaborate 

 list of synonyms given in index form. These are followed by tables of 

 geographical and bathymetrical distribution arranged by authors — a not 

 very convenient arrangement. The whole concludes with a bibliography. 



Polyzoa of the Black Sea.* — M. A. A. Ostroumoff communicates a 

 lengthy memoir on the Polyzoa of the Gulf of Sebastopol. He distin- 

 guishes 11 species, 6 in the zone of the Ulvas and Zosteras, 5 in the zone 

 of Phyllojihorefe. 



I.' In his general introduction the nomenclature and general features 

 are discussed ; he distinguishes the calcareous Cheilostomata from the chiti- 

 nous Ctenostomaia. In the former the typical zooocium is a tetragonal box. 

 Of the two transverse faces, that with the orifice is termed " opercular " or 

 " pallial," and that by means of which the colony is fixed — " basal." The 

 orifice does not always open in the centre of the opercular face, but near 

 one of the sides, which he terms " distal " or superior, while the opposite 

 one is termed " proximal " or inferior. The Cheilostomata have a semi- 

 circular operculum ; the Clenostomata have none. The modifications in 

 various subdivisions are briefly noted. Among ovicells the author dis- 

 tinguishes (1) those forming an integral part of the colony, with the whole 

 zooecium (except the digestive tube) subordinated to containing the ova 

 formed at the expense of the nearest complete zooecia ; and (2) those acting 

 rather as organs, and occurring on certain zooecia only during sexual matu- 

 rity. The Cheilostomata are covered with spicules, which probably increase 

 the respiratory surface. The skeleton of the zooecium exhibits pores on 

 the basilar surface, opening communication between mother and daughter 

 zooecium, or on the lateral surface connecting adjacent zooecia, or thirdly, 

 on the opercular face communicating directly with the exterior. Nine 

 species are then diagnosed at some length. 



II. Anatomical results, (a) Derivatives of the ectoderm. — On the poly- 

 zoon larva or young bud a delicate ectoderm is readily detected below the 

 cuticle. This soon exhibits a sort of cellular separation ; tlie nuclei go 

 apart ; the protoplasm gathers round them and forms irregular prolonga- 

 tions, and a reticulated appearance results. The great difficulty of perfect 

 fixing has led to varied descriptions by different observers. The skeletal 

 development is then described, and the means taken to secure cfiBcient re- 

 spiration are noted. Internally the ectoderm gives origin to the epithelial 

 membrane of the tentacular sheath, to the stomodaeum, proctodseum, superior 

 cells of the tentacles, and nervous ganglion. These are then discussed in 

 order. 



(h) Derivatives of the endoderm. — The median portion of the alimentary 

 canal, viz. the stomach, with its ciliated pyloric portion and cpecal appen- 

 dage, are of endodermic origin. The stomach proper lies between the 

 cardiac thickening and the pyloric chamber. With the endoderm there is 

 further associated the " brown mass," which has been so variously inter- 

 preted as ovary, embryonal capsule, &c. It is doubtless a stomachic caecum 

 in which the ordinary secreting function of the cells has been replaced by 

 that of assimilating the products of cellular degeneration. The brown 

 mass includes not only the ciecum and detritus, but a button-like mass of 



♦ Arch. Slav, de Biol., i. (18S6) pp. 557-69 (5 pis.) ; iL (1886) pp. 8-25, 184-90. 



