STOMODAEUM AND MEDULLARY TUDE 



17 



motor function supplying the voluntary musculature from 

 the myotomes. This condition is found in Amphioxus 

 where indeed HATSCHEK (1892, p. 141) and VAN Wyhe 

 (1893, p. 171) demonstrated that the splanchnic musculature 

 is supplied by branches from the dorsal nerve roots 

 {Rami viscerales). The ventral roots, supplying the striate 

 musculature, here exhibit a more or less diffuse character, 

 each springing with a great number of roots from the medulla. 

 Now there is much to be said for the conception that 

 the voluntary, striate, musculature is a new acquisition of 



yentr. 9angl. chai n 



splanchnopleura 



musc.longit- 



ventr. 



musc.Iongit. 

 dorsales. 



Fig. 4, Transverse section through the trunk of a young 

 Polyqordias, after Hatschek, 1878, lig. 89. 



Vertebrates with regard to Annelids, a special differentiation 

 from part of the smooth musculature of Annelids. From 

 here to the conclusion that the ventral nerve roots sup- 

 plying the striate muscles are also a new acquisition is only 

 one step, and then BALFOUR s original view would still prove 

 to be ultimately correct, equally with VAN Wyhe's opinion. 

 Musculature and its innervation. — The first beginning of 

 the striate longitudinal trunk musculature, of the myotomes, 

 can perhaps be already recognized in Annelids. Here we 

 can distinguish the ventral and the dorsal longitudinal 

 musculature. The rudiment of the former separates very 

 distinctly from the rest of the mesoderm and in transverse 

 sections reminds one vividly of the myotomes of Vertebrates, 



2 



