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diffuse form as in Amphioxus, have originated. In this 
connection the following observation of FRAIPONT (1884, 
_p. 281) is noteworthy: “J'ai constaté sur des coupes trans- 
versales et verticales, dans la profondeur de la couche 
epithéliale de l'oesophage à droite et à gauche chez le 
Protodrilus, chez le Polygordius et chez le Saccocirrus, qu'il 
existe, à une place déterminée, une masse d’ une substance 
finement granuleuse, entourée de noyaux de cellules un peu 
différents de ceux de Pépithélium. Je n'ai pu voir les rap- 
ports de ces deux masses ni avec le cerveau ni avec la 
moelle, ní avec le plexus intermusculaire et cependant elles 
me paraissent de nature nerveuse, d'après leur aspect général. 
Je me contente de consigner ce fait, sans pouvoir entrer, 
pour le moment, dans d'autres détails”. 
our conclusions until now are right, we ought to 
assume that originaliy 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 FRAIPONT'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 
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. 
