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single copulatory organ (see fig. 16). The anterior 

 appendage (p. 1) is tubular, and into the tube the 

 posterior rod-like appendage (p. 2) is inserted during 

 copulation. The copulatory organ of each side is 

 introduced into one of the vulvae of the females during 

 fertilisation. The genital papillae of the male are too 

 short to reach the vulvae, and the abdominal appendages 

 have become modified to form sexual organs in conse- 

 quence of this. During copulation each genital papilla 

 fits into the base of the tubular appendage and the 

 spermatophores are poured into the tube. The rod-like 

 second appendage is constantly working up and down the 

 tube, and thus forces the male sexual products into the 

 spermatheca of the female. 



The testes (test.) are paired and symmetrical, and the 

 two halves are connected immediately behind the fore- 

 gut. Each testis is a compact lobulated organ situated 

 in the antero-lateral region of the cephalothorax. It is 

 superficial in position, and lies immediately below the 

 dermis and above the digestive gland. The size and 

 shape of the testis varies considerably according to the 

 condition of the animal. In immature crabs it may be 

 extremely small, but in the mature specimens the testis 

 is massive and lobulated, and may cover almost the whole 

 of the digestive gland. Its blood supply is obtained from 

 the large spermatic branch of the lateral artery. At its 

 inner extremity, near the cardiac fore-gut, each testis is 

 connected with the vas deferens (v. d.). The main part 

 of the testis gives off a posterior branch which passes 

 backward beneath the vas deferens alongside the mid-gut 

 caecum. Above the mid-gut this prolongation turns 

 inward and joins with the similar portion from the other 

 side to form a bridge behind the pyloric fore- gut. 



The mm deferentia are a pair of long convoluted 



