370 C. JUDSON HERRICK 



The details of the bulbar and spinal connections of the neurones 

 of the area acustico-lateralis I have not been able to determine. 

 Throughout the length of the oblongata there is a tract of fibers 

 dorsally of the bulbar lemniscus arising in part from the motor 

 tegmentum of the same and the opposite side which increases 

 rapidly in size as it passes from in front caudad. This is the 

 tractus bulbo-spinalis (figs. 10 to 17, tr.b.sp.), and it is probable 

 that descending fibers from the area acustico-lateralis and other 

 sensory centers of the oblongata are also associated with this 

 tract for bulbo^-spinal reflexes. 



The neurones related with the VIII roots are of the same type 

 as the preceding, and I have seen no case of a neurone related to 

 endings of the VIII nerve which does not also send a dendrite 

 into the lateral line roots or into the spinal V root or both. No 

 evidence of specially differentiated cochlear or vestibular nuclei 

 has been found in the larva, but in the adult such differentiated 

 cells are manifest. The peculiar relations of Mauthner's cell 

 will be considered beyond (see p. 379). 



A typical neurone of the sensory V nucleus under the eminentia 

 trigemini at the level of the superficial origin of the root is seen in 

 figure 24. The chief dendrite spreads out in the distribution area 

 of collaterals from the root fibers (cf. figs. 49 and 50), but other 

 dendrites enter the areas of the VIII root and of the tractus 

 spino-bulbaris et tectalis. Still other dendrites enter the marginal 

 zone of gray substance, where they may engage termini of arcuate 

 fibers. In figure 23 an incomplete impregnation of three similar 

 neurones is seen, the axon being directed downward into the 

 ventral commissure. In figure 25 is another group of these 

 neurones, whose dendrites reach the sensory V fibers, the ascend- 

 ing secondary visceral tract, the tractus spino-bulbaris et tectalis 

 and also the underlying tegmentum. An exactly similar neurone 

 from a level slightly farther rostrad. is seen in figure 22. In this 

 case a dendrite also enters the field of VIII root fibers. Still 

 farther forward under the cerebellum (fig. 21) are two neurones 

 of the eminentia cerebelli ventralis which are apparently of the 

 same type, the dendrites ending chiefly among the fibers of the 

 sensory V root and the tractus spino-bulbaris et tectalis. Again 



