TESTIS IN DECAPODOUS CRUSTACEA. 429 



XXVI. THE TESTIS AND ITS SECKETION IN THE 

 DECAPODOUS CKUSTACEANS. (PLATES VII. VIII.) 



THE organs of generation in the male crustacean consist of 

 testes, vasa deferentia, and external or intromittent organs. 



In no class of animals do these parts vary so much as in 

 that now under consideration. In every family, and almost 

 in every genus, they afford generic, and in some even specific, 

 characters. This variableness of configuration and structure 

 is not peculiar to the organs of reproduction, but exists also 

 in the other systems the vascular and respiratory, the 

 nervous and locomotive. Such a variableness is to be looked 

 for in a class, the forms in which pass from that of the 

 annelids, through the articulata, to the mollusc. Through- 

 out all this range of form the organs and functions vary in 

 accordance with those in the group of animals to which the 

 crustaceans presenting them are analogous. 



In all the higher, or Brachyurous Crustaceans, the internal 

 organs of generation are comparatively most highly developed. 

 These organs exhibit the greatest complexity of form and 

 structure among the Triangulares, but in the next order, the 

 Cyclometopa, they are of great size. These crustaceans are 

 accordingly the most prolific, and in' greatest demand as 

 articles of diet. The Catometopa, or rather the higher forms 

 of that family, have these organs also very large ; this family 

 containing the land-crabs of tropical climates, which are used 

 as food. 



As we descend towards the Anomoura, the internal organs 

 of generation are found to give way gradually to others, which 



