ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 413 



but with eye-stalks modified as sharply pointed rostra. Examples of 

 the first type were not found in the collection, but Lankester believes 

 that "there is no doubt that such a shallow water form has existed, 

 and very possibly still exists." He further quotes evidence for believing 

 that the form with rostriform eye-peduncles has a geographical and 

 not merely a bathymetrical correlation, and ranks it as a distinct species, 

 naming it C. normani. 



Breeding Habits of American Crayfish.* — E. A. Andrews gives 

 an interesting account of the breeding habits of Cambarus affinis. 

 Though his observations were made upon individuals kept in confine- 

 ment in the biological laboratory at Baltimore, they probably indicate 

 in some measure what occurs in nature. Field observations remain 

 " much to be desired." 



In two lots the females were decidedly in the majority, 26 : 14 — 

 39 : 14. In a third lot they were 41 to 39 males. Even when the 

 females are more abundant than the males, there is no probability of 

 the eggs going without fertilisation, since one male may unite with 

 several females. 



Sexual union was observed in February, March and April, but there 

 is an autumnal pairing, in place of or in addition to the spring pairing. 



The spermatozoa are transferred from the male to an external 

 seminal receptacle upon the female, where they are stored till the time 

 that the eggs are laid. There is no copulation or use of intromittent 

 organs as in crabs, nor any such vague attachment of spermatophores 

 as has been described in the European crayfish, Astacus ; in captivity 

 the union lasts from two to ten hours, and either the male or the 

 female may repeat the process with other individuals. 



The somewhat intricate sexual union is described in detail ; the result 

 is the storing up of spermatozoa within the annulus or sperm receptacle 

 in the female. The annulus in Cambarus affinis may be described as a 

 calcified region on the ventral side of the thorax, between the sterna 

 of the somites bearing the fourth and fifth legs. The evidence strongly 

 favours the view that the seminal matter received into the annulus is 

 that which subsequently fertilises the eggs. Perhaps spermatozoa re- 

 ceived in autumn may be used to fertilise ova laid in spring. 



After sexual union many of the crayfishes died, and it was found 

 that the males died in larger numbers than did the females. In several 

 cases the males died within a few hours after union. 



After union there is quite a long period before the eggs are laid, — 

 often some weeks. In preparation for laying the females tend to hide 

 in dark corners and are very excitable. These days are taken up with 

 great and peculiar activity, resulting in a thorough cleaning of the 

 ventral side of the abdomen. This is also described in detail. The 

 eggs are usually deposited at night, and the liberation is preceded by 

 the exudation of the secretion of the " cement glands." Thus the 

 eggs pass from the oviducts into a basket formed by the bent-up 

 abdomen and full of glairy secretion which protects them from contact 

 with the water. 



* Amer. Naturalist., xxxviii. (1901) pp. 165-206 (10 figs.)- 



