THE ANIMAL KINGDOM 



15 



although we are far from knowing even approxi- 

 mately in every case the course evolution has 



act. 



Fig. 4. Transverse section through a young Vertebrate, al. alimen- 

 tary canal, end. endoderm. ect. ectoderm, c.ep. coelomic epi- 

 thelium (somatopleur) , the splanchnopleur is applied to gut and is 

 not lettered, coel. coelom. myo. dorsal myotom or muscle block. 

 n. nerve tube. not. notochord. /c. a kidney tubule or coelomoduct 

 opening into coelom by a ciliated funnel. G. gonad, only repre- 

 sented on one side. b. dorsal aorta, muse, latero-ventral body 

 muscle. 



followed, yet we are safe in concluding that all the 

 diverse ramifications have originated in the remote 

 past from some one common source, or type. But 



