ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 357 



bothria, without auxiliary suckers, costa3 or loculi. Each bothrium is 

 strengthened by a strong muscular ring, with a thin, more or less 

 leaf-like border, and is armed at the anterior end with a pair of com- 

 pound hooks. Each hook consists of two unequal prongs, which rise 

 from a flattened base. This basal part of the hook has a characteristic 

 shape in each species. The neck is traversed by conspicuous bundles of 

 longitudinal muscle-fibres. This new genus is separated from Acantho- 

 bothrium by the absence of costas, and from Phoreiobothrium by the 

 character of the hooks, which have two instead of three prongs, and 

 further by the absence of loculi on the bothria. 



Anonchotsenia.* — 0. Fuhrmann discusses this Cestode genus which 

 has many representatives in Passerine birds. There is no rostellum, 

 the jointing of the strobila is subsequent to the establishment of the 

 gonads, the genital apertures are regularly alternate, and there are 

 distinctive peculiarities in the reproductive organs. Fuhrmann de- 

 scribes eight species, of which four are new. 



Development of Prosorochmus viviparus.f — W. Salensky has 

 studied the embryos of this Nemertine, with special reference to some 

 disputed points. The mesoderm is traceable to primitive mesoblast- 

 cells, appearing near the blastopore, and probably also to mesenchyme. 

 The whole nervous system arises from a single primordium — two lateral 

 thickenings of ectoderm dorsal to the blastopore. Each primordium 

 differentiates into a dorsal and ventral portion, forming the respective 

 2;an2;lia, and the lateral nerves arise as extensions from the ventral 

 ganglia. In the embryo, as also in the adult, there is a coelom, 

 represented by a dorsal cavity (the proboscis sheath) and two lateral 

 cavities (due to the partial splitting of the mesodermic pleural- layer), 

 in which the lateral nerves lie. The proboscis has no share in the 

 formation of the oesophagus ; the two structures are primarily quite 

 distinct ; the atrium of the proboscis, however, is at once part of the 

 proboscis and part of the cesophagus. 



Incertse Sedis. 



Fertilisation and Development in Orthonectids.J — M. Caullery 

 and A. Lavallee have studied Rhopalura ophiocomse, and find that the 

 phenomena of maturation and fertilisation are closely comparable to 

 those in Metazoa. There is a reduction in the number of chromosomes 

 like that in Ascaris megalocephala, there seem to be tetrads formed, and 

 so on. The embryo is definitely cellular, in contrast to the plasmodial 

 later stages. Many facts set forth in the memoir point to the con- 

 clusion that the Orthonectids are organisms derived from higher forms, 

 that have been simplified as regards their vegetative organs and 

 differentiated as regards their reproductive system, both changes being 

 related to their parasitism. 



* Centralbl. Parasitenk., xlvi. (1908) Abth. i., pp. 622-31 (16 figs.), 

 t Bull. Acad. Imp. Sci. St. Petersbourg, 1909, pp. 325-40 (9 figs.). 

 J Arch. Zool. Exper., viii. (1908) pp. 421-69 (1 pi. and 7 figs.). 



