ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 575 



siphons (1) an " eye," consisting of pigment, lens, nerve, retina, and 

 argentea ; and (2) another organ, consisting of sensory hairs. He describes 

 the state of affairs in C. mi stir inn, C. muticum, and five other species. 

 In all cases the "sensory hair organ" consists of an unsunk group of 

 epitheloid sensory cells, with sensory hairs communicating with the 

 exterior. The author's experiments show that cockles do not " see." 

 Those without " eyes " react like those with " eyes." There is great 

 sensitiveness to shadows — even of clouds overhead — but it is not de- 

 pendent on the presence of " eyes." The sensory hair-organ is probably 

 an organ of chemical sense. 



Post-embryonic Development of Unio.* — W. Harms has studied 

 Unio pictorum and U. tumidus. As Lillie observed, the glochidium of 

 Unio is not so highly differentiated as that of Anodonta. The infection 

 of fishes is oftener on the gills than on the fins. The parasitism lasted 

 for 26-28 days at a temperature of 16-17° 0. Nutritive protoplasmic 

 processes from the larval mantle-cells enter into intimate union with the 

 portion of branchial tissue to which the glochidium is fixed. The author 

 compares the changes that occur during the parasitism with those 

 that have been established in regard to Anodonta, and notes various 

 differences. He shows that heart, pericardium, and kidney are all due 

 to the ectoderm. The najad-stages are also described, and the changes 

 they undergo. An interesting figure of a najad three weeks old shows 

 the larval and the definitive shell. 



Studies on Mussels. f — H. Chas Williamson discusses the develop- 

 ment of the reproductive organs in Mytilus edidis, and the appearance in 

 different months of the year. He records facts bearing on the growth 

 of the mussel, and describes its movements. An account of the struc- 

 ture of the foot is given, with special reference to the byssus pit. The 

 author has also some notes on the horse-mussel and the spout-fish (Solen 

 siliqua). 



Arthropoda. 

 a. Insecta. 



Artificial Parthenogenesis in Silk-moth. ! — Vernon L. Kellogg 

 notes that in a clutch of unfertilised eggs laid by a virgin silk-moth 

 (Bombyx mori) there are almost always some (7-8 p.c. on an average) 

 which begin to develop. In the Bagdad race 25-75 or even more begin 

 to develop. The development extends to the formation of the embry- 

 onic envelopes or further. Some collapse within a few days, some in a 

 few weeks, while a few persist for several months. The normal duration 

 of the egg-stage — from laying to hatching — is about nine mouths. 



Tichomiroff (1885 and 1902) found that by bathing the unfertilised 

 eggs with concentrated sulphuric acid, or by rubbing them gently, he 

 could increase the number that developed. He found that the develop- 

 ment was somewhat abnormal. Verson (1899) used electricity as a 

 stimulus, and Quajat used various chemical and physical stimuli also 

 with success, but his report is not clear. 



* Zool. Anzeig., xxxii. (1908) pp. 693-703 (5 figs.). 



t Fishery Board for Scotland, 25th Ann. Rep., part iii. (1908) pp. 221-55 (5 pis.). 



I Biol. Bulletin, xiv (1907) pp. 15-22. 



