ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 431 



vesicula seminalis where the latter bends round to the prostate gland. 

 It was first observed in Pteri/gioteuthis, but is present in Abraliopsis and 

 in Illex. It is of considerable length, and can be followed almost to 

 the tip of the prostate (in Abraliopsis it projects beyond it) ; it ends in 

 a ciliated funnel, which is 2 ram. long. The direction of the stream 

 caused by the cilia could not be made out, and its function is doubtful. 

 The author further discusses the morphology of the " genital pocket " 

 which surrounds the sexual glands. It has no genetic connection with 

 the body cavity, and is lined with ectoderm. 



■y. Gastropoda. 



Maturation in Enteroxenos bstergreni.*— Kristine Bonnevie has 

 made a detailed study of the maturation divisions in this remarkable 

 Gastropod parasite of Holothurians. The general conclusions are the 

 following. The apposition of each two homologous chromosomes in 

 pairs in the synapsis stage is not transitory, but persists through both 

 maturation divisions, and leads ultimately to complete fusion of the 

 two conjugating chromosomes. Both maturation divisions are equation 

 divisions, the process being complicated by the relatively large size of 

 the spindles and by the doubling of the chromosomes. By the two 

 rapidly succeeding divisions the double chromosomes are reduced to the 

 normal size, while the reduction in number occurs in the synapsis. 



Nervous System and Subradular Organ in Solenogastres.f — 

 Harold Heath has studied these in a species of Proneomenm and a 

 species of Rhopalomenia. On the ventral pharyngeal wall of the former 

 the well-developed polystichous radula is placed, and immediately 

 beneath its anterior border are two patches of high columnar cells, each 

 group being capable of retraction within a sheath, or of being everted 

 and fully exposed. Both are innervated from ganglia not hitherto 

 described, and the author seeks to show that they are probably to be 

 considered as the homologue of the sub-radular organ of the Chitons 

 and some of the Prosobranchs. The nervous system is described in 

 detail. 



Tidal Periodicity in Littorina rudis. J — Gr. Bohn finds that Littorina 

 rudis, which lives in a zone upon the shore reached by the sea only once 

 a fortnight, affords a clear case of periodicity. It alternates between a 

 period of slowed-down life, the result of anhydrobiosis, and active life. 

 This vital rhythm persists for months in aquaria, where the conditions 

 are quite different from its natural haunt. During high tides the least 

 shock provokes movement, and the animal is both geotropic and photo- 

 tropic, while at low tide the opposite is the case. 



Anatomy and Phylogeny of Haliotis.§ — H. J. Fleure describes 

 some details of the minute structure of certain organs, discussing blood- 

 vessels, stomach, left kidney, the branch of the pleuro-visceral loop, and 

 the otocysts. Regarding these and other structures, various new points 

 have been brought out. The commissure between the anterior pedal 



♦ Anat. Anzeig., xxvi. (1905) pp. 497-517 (33 figs.). 



t Zool. Jahrb., xx. < 1904) pp. 399-408 (1 pi.). 



\ Comptei Rendus, cxxxix. (1904) pp. U10-11. 



§ Jenaische Zeitschr., xxxix. (1904) pp. 245-322 (6 pla.). 



