ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 691 



of North American Uniones in the fauna of the Mississippi river have 

 descended genetically from North American fossil forms. 



Cytology and Artificial Parthenogenesis in Eggs of Mactra. * — 

 K. Kostanecki has carried out experiments with various alkaline salts, 

 and with different degrees of concentration of sea- water, and has been 

 successful in initiating development. His observations included a study 

 of sections of the developmental stages induced as well as the living 

 material. Those eggs which were treated with a solution of potassium 

 chloride approached most nearly in their development to the behaviour of 

 fertilised eggs. The author considers that by a suitable arrangement of 

 the conditions, such as concentration, length of time in the fluid, and so 

 on, a reproduction of the normal results might be achieved. The 

 experiments indicate the lines along i which future inquiries should be 

 directed. 



Adductor Muscles of Mactra and Pecten.f— F. Marceau has studied 

 the mechanical work done by these muscles. They only do their maxi- 

 mum in a given time when they have to overcome an external resistance 

 (the water) in addition to their action on the ligament. The vitreous, 

 more or less rapidly contracting portion of the muscle, closes the shell ; 

 the nacreous, more or less slowly contracting portion, keeps the valves 

 closed. 



Structure of the Pearl Oyster.} — W. A. Herdman gives a full 

 description of the structure of the Ceylon pearl oyster, Margaritifera 

 vulgaris Schum, with notes on the habits and functions of the living 

 animal. 



Arthropoda. 

 a. Insecta. 



Poison in Bees' Eggs.§ — C. Phisalix has shown that in the toad 

 and the viper the specific poisons accumulate in the ova, and has 

 suggested that they play an important part in the phenomena of de- 

 velopment and inheritance. He now shows that in bees the ova contain 

 small quantities of poison. It required 475 eggs to furnish enough to 

 poison a sparrow. Phisalix tackles the difficulty that the unfertilised 

 poison-containing egg gives rise to a drone without poison. To allow 

 of the development of a poisonous female the poison " determinants " 

 in the ovum require to be supplemented by something furnished by the 

 spermatozoon or by the accessory male glands. 



Habits of Gerydus chinensis.|| — J. Kershaw gives interesting notes re- 

 garding some of the habits of this butterfly. The female deposits her eggs 

 upon the branches of the bur-marigold, Biclens piJosa. These branches 

 are covered with aphides and ants, which she thrusts aside with a brush- 

 ing movement of her tail, immediately laying a single egg. The ants do 

 not appear to meddle either with the butterflies or the eggs. The larva3 



* Arch. Mikr. Anat., Bd. 64 (1904) pp. 1-98 (5 pis.). 



t Comptes Kendus, cxli. (1905) p. 27S. 



j Ceylon Pearl Oyster Report, Royal Society, Part ii. (1904) pp. 37-76 (9 pis.). 



§ Comptes Rendus, cxli. (1905) pp. 275-8. 



|| Trans. Entomol. Soc. Lond. (1905) pp. 1-4 (1 pi.). 



3 A 2 



