236 HOWARD AY ERS. [Vol. IV. 



According to Stieda, the general shape of the cells during 

 life is that of an irregular star. 



It is not at all difficult to find, in the preserved Amphioxus, 

 cells with several pigment processes, and often the length of 

 the processes exceeds twice the diameter of the central mass. 



I. The pignie7it of the axial ftervoiis system of Amphioxus is 

 in process of m.igration totvards the anterior end of the body — 

 toivards the eye. 



Where the eye is large, the interspace between it and the first 

 pigment group is long, and vice versa. With the increasing 

 opacity of the body walls, of the sheaths, and of the central 

 nervous system itself, correlated with an increase in the degree 

 of complexity and heightening of the function of the light- 

 perceiving organs, the pigment cells scattered throughout the 

 entire length of the neural axis migrate to the eye, and become 

 associated with the percipient layer. 



The interspace between the eye-spot and the first group of 

 pigment bodies is dependent upon the size of the eye-spot — 

 i.e. upon the sufficiency of its function for the body. 



Stieda describes the pigment bodies as lying mostly in a plane 

 passing horizontally through the ventral wall of the central 

 canal ; I find however that the cells oftentimes make their way 

 dorsad along the walls of the canal, and may send processes 

 outward from the canal reaching quite to the periphery of the 

 cord. 



J. Rhode s conclusion that the giant ganglion cells of the ante- 

 rior portion of the spinal cord of Amphioxus send out axis cylin- 

 ders only caudad is erroneous, and as my preparations show, 

 Stieda s observations are correct both in figure and text. 



Notwithstanding Rhode's positive assertion to the contrary, 

 I am fully convinced that the giant ganglion cells show connec- 

 tion by means of a plurality of axis-cylinders, with structures 

 lying both caudad and cephalad of them. 



K. The vertebrate ear has developed within the phylum above 



Amphioxus, and arose from one of the primary sense organs of the 



lateral line system, at a period phylogenetically later than the 



formation of the canal system of these sense organs. The ear 



