Herrick, Morphology of Brain of Bony Fishes. 6i 



logue of the nidulus ruber under the name corpus rotundus and 

 regards it as a marked peculiarity of the fish brain. Its struc- 

 ture he compares to that of the tuber olfactorius. Fritsch was 

 unable to demonstrate the exact nature of the microscopic struc- 

 ture, though he thought he discovered possible nuclei of gan- 

 glion cells amidst the meshwork of fibres and numberless gran- 

 -ules contained in the diffusely stained granular mass. That we 

 are more fortunate is due to the method of preparation and stain- 

 ing. Numerous bundles enter it or pass through it, but Fritsch 

 was unable to discover any clue to their relation to the sub- 

 stance of the body, of the. nervous character of which he was 

 nevertheless convinced The most conspicuous bundle which 

 enters the mass is that termed by Fritsch the commissura horizon- 

 talis, which Mayser claims with perfect correctness passes through 

 it on its way to the region of the posterior commissure. But the 

 body is partly surrounded and probably penetrated by a portion 

 of the dorsal peduncles or the homologue, in a general way, of 

 the tegmental radiation. The analogy in position and fibre con- 

 nections is complete when compared with the nidulus ruber and 

 we shall see that its structure is similar. Sanders describes the 

 structure as follows : " It is composed of interlacing fibres and 

 granules, in which are imbedded cell-like bodies which differ 

 greatly in size, some measuring as much as 0.07 millim. by 0.06 

 millim., some as little as 0.04 millim. by 0.03 millim.; many are 

 nearly round, others longer than broad ; they are composed of 

 loosely aggregated granules of about o.ooi or 0.002 millim. in 

 diameter, which are crowded about the circumference, leaving a 

 space in the centre, which in many cases is occupied by a 

 smooth, oval or pyriform body, having somewhat the aspect of 

 the protoplasm of a cell, but in which no nucleus is observable ; 

 sometimes this body is missing in very thin sections, there re- 

 maining only a clear space, which it has probably occupied. 

 Capillaries are occasionally to be seen passing through the loose 

 granules of the circumferential portion. What these bodies are 

 I am at a loss to determine, they are about the same size as the 

 larger cells of the spinal cord. The granules also, which com- 

 pose their cortex, resemble those of the protoplasm of those 

 cells, in size and aspect, except that they are more loosely ag- 

 gragated ; they might be looked upon as cells in which the gran- 



