1890.] Development of the Brain of Clupea harengus. 199 



(2.) That a compound exists in certain urines which under the in- 

 fluence of a fermentation yields cystin. 



(3.) That the fermentation is due to the growth of an organism, 

 which can apparently be separated from the urine by ordinary filtra- 

 tion, and must therefore be a large organism, 'possibly a torula. 



(4.) That the cases recorded in which cystin has been found de- 

 posited in the kidneys and liver indicate that the fermentation may 

 begin in the system. 



III. " Some Stages in the Development of the Brain of Clupea 

 harengus'' By ERNEST W. L. HOLT, Marine Laboratory, 

 St. Andrews. Communicated by Professor MclNTOSH, 

 F.R.S. Received February 11, 1890. 



(Abstract.) 



The stages described are (i) newly-hatched or early larval ; (ii) 

 early post-larval; (iii) J- inch long; (iv) f-inch long. 



The development of the pineal region is treated separately, and in 

 this a fifth stage — l^-inch long — is introduced. 



In the early larval stage the downward flexure of the fore part of 

 the brain is very noticeable. It appears due to the general conforma- 

 tion of head at this stage. The cerebral lobes are short ; the anterior 

 commissure is well marked. The white matter of the cerebrum is 

 divided iuto two patches on each side, from the most ventral of 

 which the short stout olfactory nerves pass to the bases of the nasal 

 sacs, now closely opposed to the cerebrum. The roof of the cerebrum 

 is very thin, passing into the thicker roof of the thalamencephalon. 

 The tips of the optic thalami are wholly vesicular. A diverticulum 

 of the 3rd ventricle extends downwards and backwards, its distal 

 extremity underlying the optic commissure. The broad ventral com- 

 missure of the infundibulum, noticed in Anarrhicas,* is well marked. 

 A commissure shuts off the lumen of the infundibulum from the 

 hind part of the 3rd ventricle immediately in front of the splitting 

 off of the infundibulum. The optic ventricles do not appear in the 

 front part of the mid-brain, and are only partially developed further 

 back. The tori semicirculares are present in the hind part of the 

 mid-brain as mounds on either side of the central fissure of the 

 cerebral mass. The valvula appears in transverse section as a pair 

 of ridges externally to the tori, before it shuts off the aqueduct of 

 Sylvias. The cerebellar fold is very short ; the pituitary body is a 

 roundish mass of deeply staining cells, opposed ventrally to the 

 membranous roof of the mouth, and clasped in front and at the sides 



* Mcintosh and Prince, ' Edinb. Roy. Soc. Trans.,' vol. 35. 



