330 FISHES. 



front, one being placed in the middle, whilst the lateral portions are 

 transversely striated. 



I found them also very considerable in the surmullets where their 

 surface is marked by tortuous furrows, like that of a brain. 



In the gurnards we have seen as many as five bosses on each side, 

 arranged in a row, rounded, occupying a space that extends as far as 

 the second vertebrae, and which, is just as long as the remainder of the 

 brain. From the latter of these tubercles, the second pair of spinal 

 nerves is given off, it terminates in the three rays which in this genus 

 are attached beneath the pectoraL 



These lobes have been compared to the little greyish band which, 

 in mammalia, is placed across -the corpus restifor me, or medullary 

 cord, which passes behind the cerebellum to the medulla, and border- 

 ing on each side the fourth ventricle ; but it must be admitted, that 

 this would be a prodigious dcvelopcmcnt of them. 



In the bottom of the fourth ventricle, slight longitudinal furrows are 

 observed, which already mark the division of the medullary fasciculi, 

 the external of which proceed to the hollow holes, and terminate at 

 the swelling (A. A), which I have called the notched body ; the mid- 

 dle ones are continued as far as the anterior lobes (c, c). We see here, 

 also, the lineaments which seem to indicate the origins of the nerves 

 of the fifth, seventh, and eighth pairs. 



There is nothing below, bearing a resemblance to the potisvctfdUi; 

 but furrows are visible, which appear to distinguish the fasciculi just 

 mentioned. The middle ones represent the corpora pyramidalia ; but 

 the fibres do not appear to be crossed. There are no corpora oli- 

 varid, .unless we wish to search' for them in the tubercles above the 

 medulla (a, (/), but in that case ' they would be much higher than in 

 mammalia. On the side of the medulla" are seen the restiform 

 fasciculi, which terminate at the ccrebulltim. 



The pituitary gland (f) is situated as usual, under the brain, at the 

 extremity of the infundibulum. In fishes, it is generally large and 

 accompanied by membranous and vascular appendages of various 

 forms. ' In the Ray, these appendages are particularly remarkable. 

 Sometimes, as in the lophius,the aigrefin, &c. the infundibulum is 

 prolonged to a thread, and the pituitary gland is placed far in front. 

 The same obscurity with regard to its use exists in fishes as in the 

 other classes of animals. 



The Nerves and Spinal Marrow. 



The olfactory nerves (a a) come from the anterior tuburcles (c, c) 

 and very often we find again a swelling at their root (i, z) : they vary 

 much in size and composition; sometimes merely capillary, sometimes 

 thick though single, and sometimes double, triple, or composed of 

 threads more numerous, which form a bundle. In many fishes, 

 they swell to the size of a ganglion before they are distributed to the 

 pituitary membrane, and it has been remarked that this happens 

 chiefly in the species where there is no swelling at their base, in 

 front of the anterior lobes. 



The optic nerves (11, n) cross each other in front of the infun- 



