ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 753 



e. Crustacea. 



Sperm Transfer in Certain Decapods.* — E. A. Andrews points out 

 that the sperm-masses may be applied to the surface of the shell (as in 

 Astacus), or directly introduced into the oviducts, or placed in a special 

 receptacle, like the pit in Gambarus. A peculiar receptacle known as the 

 " thelycum," is found in certain prawns, the Peneidoe, as also in 

 Anaspidacea. The paper describes the " thelycum " of Peneidre, in 

 Peneus and Parapeneus, where it is a cavity enclosed more or less by 

 outgrowths from the shell, and is found full of spermatozoa. In the 

 deep-sea prawns of the group Eryonidea, Geoffrey Smith has described 

 a similar receptacle, but the author shows that this interpretation is very 

 doubtful. In the species of Polycheles which he has studied he finds no 

 spermatheca. 



Development of Maia squinado.f — C. Schlegel has succeeded in 

 rearing the eggs and larvse of this crab. Its life-history is much con- 

 densed, when compared with that of Carcinus msenas, for instance. 

 From the egg there is hatched a minute Protozoaea— a transitional 

 phase which contains the first zorea. After three-quarters of an hour, 

 the first zogea is liberated. During the night of the 4th to 5th day the 

 first moult occurs and the second zoaea. Both these zoaeae live at the 

 surface and show an intense positive phototropism. During the night 

 of the 8th to 9th day, the megalopa-stage is reached, which lasts for 

 about a week. It leaves the surface and goes deeper and deeper. The 

 subsequent post-larval form has all the adult characters, and is negatively 

 phototropic. 



Palsemon niloticus in Lake Tchad. $— Sollaud and Tilho report that 

 Gaillard has discovered colonies of Palsemon niloticus Roux, in Lake 

 Tchad. They discuss the explanation of this interesting fact, and suggest 

 that the Tchad basin formerly extended (probably in Quaternary times), 

 to the south of the Libyan desert, to the Bahr-el-Grhazal, and thus into 

 communication with the Nile. There is considerable resemblance also 

 in the fishes and fresh-water molluscs of the Tchad and the Nile. 



Crustacea of Kermadec Islands. § — Charles Chilton reports on a 

 collection (83 species) from these islands, which He about half-way 

 between New Zealand and the Tonga Islands. Most of the specimens 

 belong to species already known, nearly all the marine and littoral species 

 being Australian or Indo-Pacific forms. Of especial interest is the 

 occurrence of the large Amphipod Eurythenes gryllus, whose distribu- 

 tion has attracted much attention. The author also comments on the 

 occurrence and habits of Actxomorpha erosa, Cryptochirus coralliodytes, 

 and Porcellanopayurus tridentatus. 



Crayfish Plague. || — L. Mercier and R. de Drouin de Bouville cor- 

 roborate the conclusion that the crayfish plague in the lake of Nantua 

 is due to Hofer's Bacillus pestis astaci, which also causes " lepidorthosis " 

 in fresh-water fishes. 



* Proc. U.S. Nat. Mus., xxxix. (1911) pp. 419-34 (15 figs.). 



f Comptes Rendus, cliii. (1911) pp. 480-2. 



t Comptes Rendus, clii. (1911) pp. 1868-71. 



§ Trans. New Zealand Inst., xliii. (1910) pp. 544-73 (4 figs.). 



|| Comptes Rendus, cliii. (1911) pp. 210-11. 



