PHYLUM ARTHROPODA 



229 



similarly situated to the testis ; from each side proceeds a 

 thin-walled oviduct (od), which passes downwards, without 

 convolutions, to open on the proximal segment of the third 

 or antepenultimate leg. The eggs are of considerable size. 

 The ova, when laid, are fastened to the setae on the 

 pleopods of the -female by the sticky secretion of glands 

 occurring both on those appendages and on the segments 



B 



FIG. 130. Reproductive organs of Astacus fluviatilis. A, female : B, male : od, 

 oviduct ; oe, external opening of the same ; ov, ovary ; t, testis ; , unpaired 

 posterior portion of gonad ; vd, vas deferens. (From Lang's Comparative 

 Anatomy, after Huxley.) 



themselves ; they are fertilised immediately after laying, the 

 male depositing spermatophores on the ventral surface of 

 the female's body just before oviposition. 



The lobsters, shrimps, prawns, crabs, and hermit-crabs 

 all resemble the crayfish in the number and disposition of 

 the segments, the presence of a carapace covering both 

 head and thorax, the general structure and arrangement of 



