REPRODUCTION 



51 



.NP 



Pig. 42. — AMPHIOXUS. Transverse sections of embryos at successively later 

 stages, showing origin of notochord, neural tube and mesoderm. A, section somewhat 

 anterior to the middle of the length of an embryo slightly older than that represented 

 in Fig. 38Z?. E, from embryo having two pairs of mesodermal pouches. G, section 

 near the middle of the length of an embryo having nine pairs of mesodermal pouches. 

 A, archenteron; EC, ectoderm; EN, endoderm; MES, mesoderm; NC, notochord; 

 NP, neural plate; NT, neural tube. (After Cerfontaine.) 



