518 



ZOOLOGY 



SECT. 



In the meantime the post-mandibular appendages are formed 

 in regular order from before backwards : the eye-stalks appear 

 (Fig. 412, A\ as well as the labrum (/.) and a fold on each side 

 of the thorax, which is the rudiment of the carapace (ts), and 

 gradually extends dorsally until it meets with its fellow of the 



ntes 



fib 



focd 



ctbci 



FIG. 411. Sections of embryos of Astacus. A, Nauplius-stage (cf. Fig. 410) ; B, after develop- 

 ment of thoracic appendages (cf. Fig. 412). abd. abdomen ; an. anus ; br. brain ; ect. ectoderm ; 

 end. endoderm ; ent. enteron ; lit. heart ; tnes. mesoderm ; mes.' splanchnic layer of mesoderm ; 

 mth. mouth ; pcdm. proctodseum ; stdm. stomodfeum ; th. abd. thoracico-abdominal rudiment ; 

 v. nr. cd. ventral nerve cord. (From Korschelt and H eider, after Reichenbach.) 



opposite side and covers in the cephalothorax. , The embryo now 

 consists of a nearly globular cephalothorax with a small abdomen 

 and a nearly complete set of appendages, all tucked in under the 

 cephalothorax and closely packed together within the egg-mem- 

 branes. In this condition the embryo is hatched, and for some 



