298 G. E. COGIIILL 



which goes farther in Anura than in Urodela, that is to say, 

 till all the g;anglia become fused into a common mass, whereas 

 they become two masses in the Urodela. 



This migration and fusion of ganglia involves not only a 

 shifting of position relative to each other but also a general 

 movement of the ganglia towards the brain along the path of 

 their respective roots. There is also a shifting of the otocyst 

 rostrad with reference to the point of entrance of the facial and 

 auditory roots into the brain. Such a movement of the vesicle 

 together with its expansion in growth, if carried far enough before 

 chondrification of the auditory capsule sets in, might explain the 

 fusion of all these preauditory ganglia into a common mass in 

 Urodela; but this could not explain the migration caudad of the 

 ganglion of the opthalmicus profundus, for instance, as illus- 

 trated in figures 1 to 4. There is apparent no purely mechanical 

 cause for such movement on the part of these ganglia. 



A very similar migration and a consolidation of ganglia occur 

 in the postauditory ganglionic complex as well. In adult Ambly- 

 stoma there is a single postauditory ganglionic mass which can 

 be resolved into its component ganglia only with difficulty (Cog- 

 hill, '02, p. 231 and fig. 1). In the ages studied here (figs. 1 to 

 4), however, there are two widely separated ganglionic masses, 

 one upon the glossopharyngeal and the other upon the vagus 

 nerve. Changes very like this occur in Anura according to 

 Landacre and McClellan, for they describe a rather marked 

 distinctness of the different ganglia of the postauditory complex 

 in 8 mm. embryos of Rana pipiens. The fusion of these ganglia 

 may be accounted for by the dilation of the auditory vesicle in 

 later development, and the consequent pushing caudad of the 

 glossopharyngeal ganglia upon those of the vagus. Before this 

 takes place, however, there is a perceptible migration of some 

 of these ganglia along their respective roots towards the brain, 

 although this is not as clear as the migration of the trigeminal 

 ganglia. The chief differences, therefore, between the cranial 

 ganglia of Anura and those of Urodela depend, apparently, upon 

 two factors — an active migration of the various ganglia towards 



