Turner, Alorpholoi^y of iJic Avian Brain. 119 



were of very nearly the same size as those just described. 

 Moreover, in one case the lenticular nidulus of the optic lobe 

 of one side was apparently supplied with pyramidal cells, 

 while the corresponding nidulus of the lobe of the other side 

 was apparently supplied with flask-shaped cells. In this 

 case the plane of the sections was known to be laterally 

 oblique to the base of the brain. These facts led to the 

 supposition that the dift'erence in the appearance of the cells 

 was a function of the obliquity of the plane of the sections. 

 Since it is easy to see how pyramidal cells might thus be 

 made to appear fusiform, and since it is impossible to see 

 how fusiform cells could ever be made to appear pyramidal 

 it is evident that the predominant cells of this nidulus are 

 pyramidal. 



These large pyramidal nerve cells are, apparently, not 

 the only nerve cells in this nidulus. Many of my sections 

 exhibit numerous smaller cells (Plate XVI, Fig. 7). These 

 cells appear to be pyramidal. They are very slender. Al- 

 though about as long as the typical cells of this nidulus, yet 

 they are often less than half as wide. Furthermore, they 

 have no obvious basal processes. Personally, I have grave 

 suspicions that these may be lateral sections of the larger 

 cells. But since I have not been able to demonstrate this, 

 and since in other niduli there are undoubted cases of cells 

 smaller than the typical ones, I have ventured to describe 

 these cells. Perhaps they are immature growths of the same 

 type as the the predominant cells. This nidulus is well 

 supplied with Deiter's corpuscles. 



In addition to the large bundle that lies ectad to this 

 nidulus, two sets of nerve fibres are associated with it. The 

 first set consists of several loose fibre bundles, which pass 

 from the fasciculus internus meso-cephalad through the 

 nidulus; the other is a narrow band of fibres, which lies 

 entad to this cell cluster and separates it from the following 

 nidulus. 



Niduhis sicb-pyriformis (Plate XV, Figs. 5, y-io). — This 



