ZOOLOGY AND BOTANY, MICROSCOPY^ ETC. 343 



being at the base of the tentacle below the eye. Some are spherical, 

 some ovoid, some more or less rhomboidal. Under high power some 

 show fine circular striations. J. A. T. 



Sex Phenomena in Crepidula plana. — Harley K Gould {Journ. 

 Exper. Zool, 1919, 29, 113-120, 1 fig.). The stimulus passing from 

 larger to small specimens of this peculiar hermaphrodite mollusc, causing 

 the latter to assume and retain the male phase, can be transmitted for 

 several millimetres through sea- water, though its effectiveness is reduced 

 at this distance. In three out of twenty-six cases there was indication 

 that the stimulus may be given faintly by Crepidula fornicata, a related 

 species. The stimulus acts in such a manner as to suggest that it is a 

 specific substance given off from the bodies of the animals, diffusible in 

 sea-water, but very unstable. J. A. T. 



Parthenogenesis in Paludestrina jenkinsi. — A. E. Boycott {Journ. 

 of Conch., 1919, 51). The absence of male individuals and of any 

 male anatomical elements in this species has been noticed before. 

 Evidence is now produced that parthenogenetic reproduction actually 

 occurs. In September, 1915, a number of the snails were put in a 

 small aquarium ; the many used for anatomical examination were all 

 found to be females ; young were produced which were first noticed in 

 November, 1916. On the 1st January, 1917, three minute individuals, 

 about 1 mm. long, were isolated under all proper precautions. By the 

 1st August, 1918, two of the jars (the third had got broken) contained 

 each about tvfentj jenkinsi, from infants to about half -grown, that must 

 have arisen from single individuals originally placed there. On the 

 same date four more very young individuals were isolated : A. and 

 B. from the first parthenogenetic broods, and C. and D. from the 

 original aquarium. In March, 1919, all four were about full-grown, 

 and on 8th April, 1919, a brood of young ones was found in B. The 

 mother was then examined by a complete series of microscopical 

 sections without finding any male organs or spermatozoa. There were, 

 therefore, two successive parthenogenetic generations : D. produced a 

 brood in May and C. in June. The parent D. was examined and found 

 to be wholly female. B. B. W. 



Notes on Hygromia limbata (Drap.) — Hugh Watsox (Proc. Malac. 

 Soc. Lond., 1919, 13, 120-32, 2 pi.). The anatomy of this recently 

 discovered member of the British fauna, and that of its nearest Conti- 

 nental allies, with the microscopic sculpturing of their shells, is carefully 

 described, and a new arrangement of the genus Hijgromia of Risso 

 founded thereon. B. B. W. 



Arthropoda. 



o. Insecta. 



Segregation of Germ-cells in Trichogramma evanescens. — J. 

 Bronte Gatenby {Quart. Journ. Micr. Sci., 1919, 63, 161-74, 1 pi., 

 1 fig.). In this monembryonic egg-parasite the germ-cells early be- 

 come segregated from the somatic region of the Q^g, and while the 

 somatic nuclei are, so to speak, undergoing phenomenal changes, losing 



