202 



Dr. J. Gnezda. 



[Feb. 20, 



•J-incli stage. It is thus much later in developing than in Salmo ;* 

 and the fold forming its front wall ne^er extends backwards to the 

 same degree as in that form and in Anarrhicas. This fold, in the 

 post-larval Zoarces, is thickened in its apex, and lodges a fine com- 

 missure. As pointed out by Balfour in Elasmobranchs the fold is due 

 to the upward rotation of the cerebrum. 



The fibrous tract over the 3rd ventricle in the herring is well 

 marked in the f-inch stage. It is seen to consist of fibres passing 

 upwards and inwards from the optic thalami to the middle line above 

 the 3rd ventricle, and then running forward to the stalk of the pineal 

 body. The tract has a double nature, as is readily seen in vertical 

 longitudinal sections of a herring lyV inch long. It is seen here to 

 be a backwardly directed fold of the brain roof, continuous ventrally 

 with the back wall of the pineal stalk, and dorsally with the roof of 

 the optic ventricle, the apex of the fold being the posterior commis- 

 sure. Its length in this form is due to the flattening of the brain, 

 the tract being very short in Zoarces, where the brain is not flattened. 

 In Zoarces, also, from the same cause, the limbs of the fold are less 

 closely applied to each other and much thicker. 



The pineal body is roundish and solid in the early larval stage in 

 the herring. It is vertically flattened in the early post-larval stage. 

 In the -^-inch stage it is much larger and contains a lumen ; it shows 

 signs of constriction into proximal and distal elements, and the lumen 

 contains a coagulable^albuminous fluid, as in. Petromyzon.^ In the 

 ly^-inch stage the constriction is still visible, and the walls are 

 generally crenated. The tissues of the pineal wall are now divided 

 into three layers, and are of varying thickness. The cartilage of the 

 tegumen cranii overlies the body at this stage. The constriction of 

 the body appears to be an exaggeration of the crenation of the pineal 

 wall met with in Salmo; it has not,, probably, the morphological 

 value of the constriction of the body in Petromyzon. 



IV. " A Cyanogen Reaction of Proteids." By J. Gnezda, M.D. 

 Communicated by Professor E. A. Schafer, F.R.S. (From 

 the Physiological Laboratory, University College, London.) 

 Received December 19, 1889. 



When dry urea is heated to its melting point it gives off ammonia, 

 and a substance called biuret (C 2 N 3 H 5 2 ) remains behind. Biuret 

 is decomposed by heat into ammonia and cyanuric acid (O3N3H3O3). 



* Hoffmann, "Zur Ontogenie der Knochenfische," 'Arch. Mikrosk. Anat.,' 

 vol. 23, 1884. 



f Beard, "Parietii Eye in Cyclostomatous Fishes," 'Quart. Joum. Micros. 

 Sci.,' 1889. 



