220 bulletin: museum of comparative zoology. 



pass upward between the sense cells. At their terminations they turn 

 backward, forming a loop. A far greater number of fibres, however, 

 are described as passing to the bases of the sense cells, where the 

 fibrillae separate from one another and appear to clasp the cells as a 

 bird's claw clasps a ball. This appearance, however, they believe to 

 be due to incomplete impregnation. Cases are described in which only 

 a few fibrillae are stained ; these attach themselves to the surface of the 

 cell, but can be followed only to the level of the upper surface of the 

 nucleus. Besides these, they reproduce structures in which the w^hole 

 cell body is enwrapped in the finest terminal twigs, which appear to be 

 bound together by delicate anastomoses. Finally, cells are frequently 

 found which are enclosed from base to periphery with a close-meshed 

 trestle-work of larger and smaller fibrillae. They believe that these 

 difterent appearances are due, not to the existence of different modes of 

 termination, but rather to differences in the completeness of impregna- 

 tion, and that the more numerous and more simple structures are 

 incompletely impregnated, and that the rarer pericellular networks 

 represent the universal terminal structure. I take it that they regard 

 this structure as identical with the terminal expansion which has been 

 referred to as a calyx structure. It is declared that the pericellular end 

 structures, described by Ramon y Cajal as restricted to the summits 

 of the cristae, have been found by them in all parts of the cristae, and 

 are abundant in the maculae as well. Occasional sense cells are found 

 which contain within them a definite ring-shaped body, stained like 

 the axis cylinders. The microchemical behavior of this body leads 

 these investigators to regard it as nervous in character. Examples 

 were found in which this endocellular ring was connected with the 

 pericellular network by a fibrillar bridge. The authors believe that 

 in this structure they have found an altogether unique end-organ within 

 the sense cell. They suggest the probability that this structure acts 

 as a transporting mechanism which communicates the movements of 

 the protoplasm of the sense cell to the fibrillae lying on its outer surface. 

 The relation between sense cell and axis cylinder is not in their opinion 

 one of contact; they prefer to describe it as one of concrescence. In 

 the hope of being able to ascertain whether this intimate union between 

 sense cells and axis cylinders is primary or secondary, they examined 

 the conditions in two human embryos. One of these was obtained at 

 the beginning and the other at the close of the second month of preg- 

 nancy. It was found that many of the primitive cells of the forming 

 ganglion of Scarpa show processes, some of which are directed toward 

 the periphery and some toward the brain. In consequence the investi- 



