No. 447] BREEDING HABITS OF CRAYFISH. 171 



water the two may be fixed in almost normal positions and serve 

 to make most excellent museum preparations/ 



Bound together in this way the transfer of sperm from male 

 to female takes place during several hours. Smcc ihc na\ fish 

 may now be roughly handled or transferred from one dish to 

 another there is little difficulty in observin-- how the sperm- 

 transfer is effected and a lens may be used without causing; the 

 union to cease. The terminal part of the \as defeieus of the 

 male, on each side, is found in this period of union to protrude 

 horizontally into the water from the base of each fifth leg as a 

 short, soft, bent tube of translucent appearance. This organ fits 

 exactly into the beginning of the long groove that passes down 

 the first male pleopod, right or left. These pleopods are in fact 

 massive, calcified and rigid tools, each with a deejD sinuous groove 

 along it that is seen to lead the sperm from the above ending of 

 the vas deferens down to the tip of the pleopod. The special- 

 ized, sharp tips of these organs are inserted into the annulus. 

 The sperm seen to issue from the vas deferens tube glides down 

 the groove of the pleopod to the annulus in the form of long, 

 macaroni-hke cords. Microscopic examination of these cords 

 reveals a central axis of real sperm made up almost entirely of 

 the sperih cells and an outer tubular case comparable to soft 

 macaroni. During this transfer of sperm the tip of each pleopod 

 of the second pair is closely applied to the pleopod anterior to it, 

 but no observation was made upon the mode of action of these 

 second pleopods. Each of them has terminal filaments that may 

 well be sensory and also a peculiar, soft, somewhat triangular 

 "spoon " or scoop that fits nicely against the groove of the hr.st 

 pleopod. It would seem that the second pleopotls may act to 

 convey sensory impressions and to protect and guide the sperm 

 masses which were found not to go astray but to be in some 

 way retained in the grooves of the first pleopods and forced on 

 into the annulus, probably with the guidance and direction of the 

 second pleopods. 



Probably both sides of the body in the male are active at the 



