284 



into a space completely encircling the tip of the bulbus. Through the 

 septa the parenchym surrounding the ductus meets with that of the 

 bulbus proper. 



This complexity of structure can of course only be clearly ex- 

 hibited by drawings. 



I shall make mention of only one more organ — namely the vitella- 

 ria which consist of a longitudinal canal on each side of the intestine 

 from whose sides pass off numerous short ducts, the necks of the flask- 

 shaped follicles : about two thirds of its length from the anterior end 

 each longitudinal canal bends downwards and gives off the transverse 

 canals figured by Voeltzkow and which unite at the vitelline sac 

 to form the unpaired vitelline duct. 



4. On the Conjugation of Cambarus. 



By E. A. Andrews , Baltimore. 



eingeg. 7. Mai 1895. 

 Some observations upon the breeding habits of Cambarus afßnis 

 show that there are important differences between the American cray- 

 fish , Cambarus , and the European crayfish Astacus and that certain 

 structures hitherto known only as specific and generic characters are 

 necessary accessory reproductive organs. 



1) When kept in confinement Cambarus afßnis conjugated in 

 November and in February, March and April. 



2) The process lasts several hours. 



3) The male exhibits great skill and persistency and is visibly 

 excited throughout the process while the female is from the first pas- 

 sive and inert and shows scarcely any evidence of excitement. 



4) The sperm is introduced into the cavity in the aiiuulus, which 

 thus serves as a sperm receptacle as in the lobster, Homarus america- 

 nus^ as described by Professor Bump us (Journal of Morphology, V. 

 1891.) 



5) The well known hook on the ischiopodite of the third walking 

 leg of the male is used in the process of conjugation to firmly attach the 

 male to the female. The tip of the hook depresses the membrane be- 

 tween the coxopodite and the basiopodite of the fourth walking leg of 

 the female and the hook catches firmly against a stiff ridge on the 

 basiopodite. 



6) The sperm is conveyed down the groove of the stylet or first 

 pleopod of the male from the penis-like everted end of the vas defe- 

 rens into the cavity of the annulus of the female. The annulus be- 

 comes filled and a plug of sperm and protective secretion projects from 

 its orifice after conjugation. 



