430 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS. 



have apparently a more important part to play in the economy ; 

 and in the lowest forms of the Oxystoma they are in a 

 minimum state of development. 



In this division (BracJiyura) they occupy both sides of the 



shell, lying upon the liver, and sometimes entering the folds 



.of that organ, and separated with difficulty from it. In 



others, as Cancer and Carcinus, when in an active state, they 



completely cover and conceal the liver. 



In Leptopodiimi and Hyas the testis is a body of consider- 

 able size, lying upon the upper surface of the liver, and con- 

 sisting of irregular masses, formed by the twistings of its 

 constituent duct. It is covered by a delicate membrane, 

 which is much stronger on the body of the testis than else- 

 where, and is analogous to the tunica albuginea in the higher 

 animals. The gland, extending forward, gradually enlarges, 

 and when it has arrived in a line with the stomach, curves 

 slightly inwards to the mesial plane, and terminates in a large 

 tube on each side, which is its duct much dilated. This large 

 tube, making a number of convolutions, proceeds inwards and 

 downwards until it meets and forms a junction with that of 

 the opposite side. The anastomosis is incomplete in this 

 division of the class. After running in contact for some 

 distance, the two ducts again separate, and each becoming 

 much smaller, terminates by opening at the base of the ex- 

 ternal organs. 



In the Anomoura, instead of being situated in the thorax, 

 as in the Brachyura, the testes are contained in the abdominal 

 segment of the body, lying on and above the liver. They are 

 very small in all the animals of this section, the tubuli 

 seminiferi being large, and after making a few convolutions 

 ending in the vas deferens, which opens on the base of the 

 fifth pair of legs, without the intervention of an intromittent 

 organ. The elongated acini are confined to the lower part, 

 and are contained within the external tunic of the gland. 



