No. 447 ] BREEDIXG HABITS OF CRAYFISfL 169 



the next move which is as follows : the male rises uji away troni 

 the female, but still holding all her claws, and deliberatcl\- passes 

 one of his fifth legs across under his body so that it projcrls 

 from the other side. When the male again settles down against 

 the female it is found that the i)leopods have the position shown 

 in the figure, whereas before this move they had the iMiinal 

 position, being directed forward, horizontally under tlie thorax 

 of the male. 



It is this forced and remarkable position of the tilth leg whieli 

 secures the necessary elevation of the male pleopods. 1 hese 

 pleopods might be compared to the blade ot a pen knife halt 

 open and tending to shut up into the handle when pressuie is 

 exerted against the tip : and as such a blade might be helil m 

 position by a pencil placed across between the blade and the 

 handle and held there, so the pleopods are held in position by 

 the crossed leg which lies anterior to them and between them 

 and the thorax of the male. All these parts are firm and rigid 

 and the pleopods articulate only where they hinge to the 

 abdomen. As the male draws himself down with force against 

 the female the pleopods are so held by the above device, that 

 their tips enter the annulus of the female and the pressure so 

 exerted would tend to shut them down into their resting posi- 

 tion, but this is opposed by the fifth leg which blocks the 

 pleopods firmly. That there is force exerted by the tips ot 

 the pleopods against the annulus was shown m the case ot a 

 female that had been reared from the egg m the Laboratory 

 and when put with a male in April of her seeoiu \eai 

 covered by a dark blackish deposit after wintering. It was 

 soon found that in union with the male the edges ot the opening 

 of the annulus had been scraped clean of the 

 stood out conspicuously against the rest of the dai ■ e.\o > i aon. 



Though the male always uses one of his fifth logs as an 

 , , 1.,.-,- cpvml or"-an it is not alwavs the 



apparently necessary seconoais st.xuai . 

 r^tor Lleft; males were seen with right j-th 

 left legs so used. Whether the use 

 each male by circumstE 

 or whether inherent in the strud 

 determined, but a student who kept 



whether 



