DEVELOPMENT OF JULUS TEKEESTEIS. 285 



or anal segment (d) being still indistinct. The four thoracic segments, 

 moreover, now exhibit on their ventral surface little nipple-shaped pro- 

 tuberances, three of which on each side are the rudiments of future legs. 

 No internal viscera are as yet distinguishable, the whole embryo being 

 still a congeries of vesicles, or cells, in the midst of which some faint 

 traces of a future alimentary canal seem to be indicated. In this state 

 the body of the embryo is completely enclosed in a smooth and perfectly 

 transparent membrane (fig. 141, A, e), which seems to contain a clear 



Fig. 141. 



Development of the embryo in Julus terrestris. (After Newport.) 



fluid. This membrane Mr. Newport regards as the analogue of the 

 amnion the vitelline or investing membrane of the embryo in the higher 

 animals, and identical with the membrana vitelli, or proper membrane of 

 the yelk. It is a shut sac that completely invests the embryo, except at 

 its funnel-shaped termination at the extremity of the body (fig. 141, A, d), 

 where it is constricted, and, together with another membrane (which 

 in the unburst egg is external to this and lines the interior of the shell), 

 assists to form the cord or proper funis (d) that enters the body of the 

 embryo at the posterior part of the dorsal surface of the future ante- 

 penultimate segment, where the mucro or spine exists in the adult animal. 

 (734.) A new process is now about to commence the development of 

 new segments. Up to the present period the posterior part of the body 

 remains less distinctly divided into segments than the anterior, the first 

 five segments being the most distinctly marked ; the sixth and seventh 

 now become more defined. It is in the membrane (fig. 141, c,/) that 

 connects the seventh with the eighth segment (at the posterior margin of 

 which last the funis (d) enters, and which is permanent as the penulti- 

 mate segment throughout the life of the animal) that the formation of 

 new segments is taking place. At this period it is only a little, ill- 



