]878.J A.Sanders. Anatomy of Central Nervous System. 415 



III. "Contributions to the Anatomy of the Central Nervous 

 System in Vertebrate Animals. Part I. Ichthyopsida. 

 Section 1. Pisces. Subsection 1. Teleostei." By Alfred 

 Sanders, M.R.C.S. Communicated by Professor Huxley, 

 Sec. U.S. Received May 7, 1878. 



(Abstract.) 



The brain of Mugil cejphalus consists of three pairs and one nnpaired 

 tuberosity above, and two below. 



The most anterior pair are the olfactory lobes. From the anterior 

 to posterior end they present four layers ; first, olfactory nerve 

 fibres with cell-like swellings upon them ; second, coarsely granular 

 neuroglia, with incipient glomeruli olfactorii, and large tripolar nerve 

 cells ; third, small usually unipolar cells each in its own space in the 

 neuroglia ; the whole collected into a rounded mass ; fourth, nerve fibres 

 proceeding from this mass to the second pair of tuberosities, the cere- 

 bral lobes, which consist of finely granular neuroglia, in which small 

 cells are situated towards the circumference, and larger cells towards 

 the centre, each of the latter contained in a lymph space. 



The third pair of tuberosities, the optic lobes, corresponding with 

 the corpora quadrigemina, are formed of a thin layer of nervous sub- 

 stance, enclosing a ventricle ; this layer, the tectum, consists of seven 

 strata : first, granular neuroglia ; second, oblique fibres with fusiform 

 cells ; third, radiating fibres ; fourth, oblique fibres ; fifth, transverse 

 fibres ; sixth, cells of a small size ; seventh, connective tissue with an 

 epithelial lining to the ventricle of this lobe. Within this ventricle, 

 on the floor, are two tuberosities, tori semicirculares, faced with con- 

 nective tissue, and containing small unipolar cells arranged along the 

 margin. Behind, the ventricle in question is closed by a process from 

 the unpaired tuberosity (cerebellum), which occupies the position of 

 the valve of Vieussens ; this is the valvula cerebelli ; it forms a fold in 

 the ventricle, and joins a longitudinal ridge situated along the con- 

 tiguous inner margins of the tecta ; on the side of the valvula are 

 processes more or less developed in different fishes. 



The unpaired tuberosity is the cerebellum ; it has a structure com- 

 parable to that of the cerebellum of the newly-born human infant. 



The tuberosities below are the hypoaria, which receive fibres from 

 the ventral surface of the medulla oblongata behind, and from the 

 cerebral lobes in front. Between the two hypoaria is the pituitary 

 body, and also a saccus vasculosus. 



The medulla oblongata behind the cerebellum has two tuberosities, 

 constructed in the same way as the tori semicirculares ; they are the 

 vagal tuberosities. 



