348 ASELLIM. 



and 8, the embryo is now nearly arrived at its full 

 development, the legs exhibiting traces of articulation, 

 and the lateral appendages having lost their trilobed ap- 

 pearance ; the mandibles, two pairs of maxillae, foot, 

 jaws, and branchial plates, and the terminal appendages 

 of the tail are visible in figure 8 ; lastly, in figure 9, 

 the embryo is seen in its final stage, with the large 

 lateral antennae articulated, and the lateral appendages 

 entirely lost. In figures 6 and 9 it will be observed 

 that there are only six leg-bearing segments, and six rudi- 

 mental pairs of legs, whilst there are seven segments and 

 as many pairs of legs in the fully developed animal ; 

 Rathke affirming that (t le dernier de ces anneaux et 

 sa paire de pattes ne se forment qu'en peu de terns apres 

 la sortie du jeune de la cavite incubatoire " of the 

 mother ; he, however, asserts that the wanting seventh 

 segment is produced by the division into two parts of 

 the sixth segment before the first moulting of the ani- 

 mal, but admits that the formation of this last pair of 

 legs "m'est restee assez obscure," partly because it is 

 effected very rapidly, and partly because the other legs, 

 being long, cover all the hind parts of the body.* 



We have ourselves examined the earliest stages of 

 these animals, and our observations agree with those of 

 Rathke, except that in the early embryonic condition 

 the lateral appendages appeared to us to be entire, with 

 a rounded terminal knob, instead of being tripartite, and 

 that in the state corresponding with that of our lower 

 right-hand figure, the upper pair of antennae are free, 

 as in figure 9, and that the external sac-like appendages 

 were associated with the hepatic lobes. 



* This circumstance is of considerable importance, viewed in connection with 

 the question of the number of legs in the early stages of Entoniscus and 

 Cryptothiria (Liriope). 



