304 THE BRAIN OF THE TIGER SALAMANDER 



In addition to these four well-defined components, there are un- 

 myelinated fibers which descend from the tectum and dorsal teg- 

 mentum through the gray and deeper layers of the alba to the region 

 of the nucleus of the III nerve (fig. ^2, tr.t.ped.). Some of these tecto- 

 peduncular fibers decussate in the ventral commissure both before 

 and behind the fovea isthmi. In Necturus some fibers of the nervus 

 terminalis probably decussate in the commissure of the tuberculum 

 posterius (McKibben, '11), and this may be true in Amblystoma. 



COMMISSURA VENTBALIS 



The ventral decussations of Necturus were analyzed in the paper 

 of 1930 (p. 89), and those of Amblystoma are similar. For the details 

 the reader is referred to that description and to a later contribution 

 on larval Amblystoma ('396). 



