STOMODAEUM AND MEDULLARY TUBE 19 



diffuse form as in Amphioxus, have originated. In this 

 connection the following observation of FRAIPONT (1884, 

 p. 281) is noteworthy: "J'ai constate sur des coupes trans- 

 versales et verticales, dans la profondeur de la couche 

 epitheliale de I'oesophage a droite et a gauche chez le 

 Protodrilus, chez le Polygordius et chez le Saccocirrus, qu'il 

 existe, a une place determinee, une masse d' une substance 

 finement granuleuse, entouree de noyaux de cellules un peu 

 differents de ceux de I'epithelium. Je n'ai pu voir les rap- 

 ports de ces deux masses ni avec le cerveau ni avec la 

 moelle, ni avec le plexus intermusculaire et cependant elles 

 me paraissent de nature nerveuse, d'apres leur aspect general. 

 Je me contente de consigner ce fait, sans pouvoir entrer, 

 pour le moment, dans d'autres details". 



If our conclusions until now are right, we ought to 

 assume that originally the striate musculature of Vertebrates, 

 in the same way as the visceral musculature, has been 

 supplied by the dorsal spinal nerves, though already in 

 primitive Annelids, as we see from FRAlPONT's observation, 

 a double innervation occurs. Such a double innervation 

 now has been demonstrated recently also in Vertebrates. 

 Here also, as has been shown especially by the researches 

 of BOEKE (1911, 1913), a double innervation of the 

 voluntary musculature is found, these muscles being 

 supplied not only by the medullated fibres of the ventral 

 roots but also by non-medullated sympathetic nerve-fibres 

 which probably serve especially for sustaining the muscle 

 tonus. Wide opportunities exist here for further investigation, 

 also in Invertebrates. 



Spinal ganglia in Amphioxus. — Our further considerations 

 will lead us to a confirmation of the generally prevailing 

 view, that Amphioxus is a form exhibiting in several 

 respects the most primitive features among Chordates. 

 So. if anywhere, we should expect to find here well- 

 developed spinal ganglia, relatively independent from 

 the medullary tube. This is not the case; on the 

 contrary, distinct spinal ganglia have until now not 

 been demonstrated in Amphioxus. After Hatschek (1892, 

 p. 140, 141) they are represented by little nests of ganglion 

 cells of a more or less diffuse character situated in the 

 cutis, close under the epidermis from which they have 

 originated, at the place where the dorsal spinal nerves 

 branch into a ramus dorsalis and a ramus ventralis. 



