590 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



When once filled the sperm receptacle holds enough to fertilize all 

 the eggs the female wall ever lay. Whenever an egg is sufficiently 

 matured it passes down the oviduct and out into the external cases. 

 As it passes the opening of the sperm tube it is fertilized, and this 

 individual fertilization is responsible for the remarkably small num- 

 ber of eggs that fail to develop. The cement glands are very large 

 and in Achtheres fill the entire sides of the thorax segments in front 

 of the genital segment. Each is crescent-shaped, its outer convex 

 surface fitting snugly inside the lateral body wall, while its inner 

 surface is nearly straight. It consists of three parts, separated by 

 well-defined constrictions. The anterior, terminal portion (0 is about 

 one-quarter of the entire length and is filled with a fine-grained matrix 



out of which is formed the cement 

 substance. This is the real glan- 

 dular portion where secretion is 

 carried on. The central half (c) is 

 a little broader than the terminal 

 portion and is somewhat flattened 

 dorso-ventrally; its wall is trans- 

 versely striated and must contain 

 muscle fibers since it is more or less 

 contractile. It is evidently used 

 for the storage of the cement sub- 

 stance until the eggs have fully 

 ripened (fig. 9). 



The posterior basal portion (6) 

 forms the duct or tube through 

 which the cement substance passes 

 out into the oviduct. It has a sharp curve or bend on its inner 

 margin around which the tube passes and wliich acts as a sort of 

 valve to regulate the flow. The cement glands of aU the other 

 genera in which they have been observed are similar to those of 

 Achtheres. 



In the male the vasa deferentia lead around the side of the stomach 

 to the ventral surface, swing back again to the dorsal surface, run 

 diagonally backward to the center of the lateral surface, turn a little 

 toward the dorsal surface, and finally pass diagonally backward to 

 the opening oh the ventral surface of the genital segment. The 

 swollen anterior portion of these convolutions is a combination of 

 cement gland and vas deferens, the fine-grained gland cells secreting 

 the viscid substance which composes the covering of the spermato- 

 phore. The posterior portion in the adult male is enlarged into a 

 receptacle wdthin which the spermatophores are gradually matured 

 and filled with spermatozoa (compare fig. 198). 



Fig. 9.— Cement glands of Achtheres am- 

 BLOPLiTis. 6, Basal poetions; c, central; 

 t, terminal. 



