178 E. A. ANDREWS. 



posterior lobe of the annulus is seen to have a convex ventral 

 surface, a somewhat concave dorsal surface and rather sharp 

 edges, right and left. The mouth of the sperm-pocket is the 

 somewhat crescentric narrow cleft, represented by the black 

 line. The bottom of the pocket is represented by the broken 

 line and the walls by the dotted lines. The pocket thus passes 

 in obliquely to the right, and its ends where they pass over onto 

 the top and bottom are bent towards the middle plane. 



The sperm-pocket here is more simple in its curves and more 

 easily seen to be a simple flat pocket than in any of the higher 

 Cambari yet studied. 



In more highly magnified sections, as in the coronal section, 

 of which part is seen in Fig. 8, the sperm-pocket is seen to be 

 made by an invagination of the simple epidermis, but the cavity 

 of this pouch is largely filled in by the thick shell which the 

 epidermis has made and which is continued in from the thick 

 shell covering the rest of the annulus. The shell keeps its 

 usual character, having a thick, laminated inner part near the 

 epidermis, a much thinner outer part that is represented as clear 

 in the figure, and an outermost cuticle that is indicated by the 

 bounding line of the figure. The cavity lined by this shell is 

 very narrow and but slightly dilated at the bottom, yet it is 

 ample to contain innumerable sperms. It is probable that in 

 life, before the action of reagents, the two sides of the pocket 

 are so firmly in contact that the cuticular layer on each side may 

 allow no water to pass into the receptacle. 



The sperm-receptacle of this crayfish is thus both very simple 

 and restricted to a small part of even the posterior lobe of the 

 annulus. In Fig. 3 the small area actually occupied by the 

 pocket is indicated by the little impitting in the posterior face 

 of the posterior lobe of the annulus, though in an exactly median 

 section this invagination would not show, as it is a little to one 

 side of the middle on the posterior edge. Fig. 7. 



The great bulk of the interior of the annulus is filled with 

 areolated, spongy tissue represented in Figs. 3 and 8, and this 

 is full of blood and scattered corpuscles, as indicated in Fig. 8. 

 No glandular nor muscular tissues were found and no nerves, 

 though special search should show nerves for the few setae 

 found on the ventral surface of the annulus, Fig. 5. 



