SPERM-TRANSFER ORGANS IN CAMBAROIDES. 263 



the diminishing terminal part of the ridge. At this level also 

 may be seen the muscle mass that extends into the endopodite 

 and indicates that the joint between the endopodite and exopodite 

 may actually be used and the position of the tip of the organ be 



Kn;. 9. 



directed by this muscle. This muscle was also seen in cleared 

 mounts in toto. 



In the same manner in C. Japonicus sections show only a 

 simple groove and large ridge, with the only difference that the 

 groove faces more toward the median aspect of the organ, so that 

 the above Figs. 7, 8 and 9 would well represent the condition in 

 both species. 



The second stylet preserves the usual pleopod form in that it 

 is forked, or has both endopodite and exopodite. In Astacus 

 {Cainbaroides} Japonicns, Fig. 10, the exopodite is a slender ob- 

 scurely segmented filament bearing few long setae while the 

 endopodite is the wide massive terminal part of the stylet. The 

 tip of this endopodite, the flabellum, bears a long tuft of setae 

 and is evidently like the tip of the exopodite, but much enlarged. 

 In the median edge of the endopodite there arises the extra ele- 

 ment comparable to the " triangle " of Cambants, that probably 

 has some use in sperm transfer. This is a thick ridge that rises 

 up as a free, thumb-like process directed diagonally across the 

 endopodite. It has a marked angular elbow on the median side 



