1/2 Journal of Comparative Neurology. 



trigeminal, a more nearly mesal group slightly cephalad of the 

 exit of that nerve. 



A comparison with the results attained by Goronowitsch 

 in Acipenser shows the relations of the ventral tracts to be very 

 similar to those set forth above. I was unable, however, to 

 trace any of the decussating fibers in the region of the eighth 

 into that nerve, of which in Acipenser he found them to consti- 

 tute one of the largest components. If indeed any acustic 

 fibers have this origin in Nectiirus, the number does not exceed 

 three or four. 



Fasciculus communis, (Osborn). — This tract has been al- 

 ready treated of at some length by Strong ('95) both histori- 

 cally and descriptively, and no extended discussion of it is 

 needed here. In Necturus this tract is relatively much smaller 

 than in Amblystonia. It first appears a short distance cephalad 

 of the beginning of the metatela as a small island of ground sub- 

 stance in the dorsal cinerea (Fig. 11) ; at the exit of the first 

 spinal nerve one or two myelinic fibers appear in it. As it in- 

 creases in size, it joins the adjacent alba, from which it is but 

 partially separated by a projection of cells dorsad of it. Up to 

 the exit of the contingent to the tenth nerve, there are but few 

 myelinic fibers in it. Cephalad of the exit of X\ it is hardly 

 distinguishable from the adjacent dorsal tracts. Between X^ and 

 IX it joins closely the myelinic fascicle called tract b. Arcuate 

 fibers penetrate, some of which turn caudad in it ; other fibers 

 from tract b turn cephalad in it and possibly may be continuous 

 with the arcuate fibers which enter it. Cephalad of the ninth 

 it is more distinct as a separate tract and is composed almost 

 entirely of myelinic fibers. Opposite the ninth a small fasci- 

 culus of fine fibers begins to form in the cinerea, dorso-mesad 

 of the fasciculus coimnunis which joins the bundle a short dis- 

 tance caudad of the seventh nerve, and with it leaves the brain 

 to form t]\Q fasciculus communis component of that nerve, (VII, 

 a. a.). I find no continuation of this bundle in Necturus cephalad of 

 the seventh as it was found by Osborn ('88) in Cryptobranchus. 



Isolated cells occur laterad and ventrad of this tract cepha- 

 lad of X\ which presumably represent what in the tadpole is 



