FISHES. 329 



the optic tubercles are hollow as in the birds. But the hemispheres 

 are also hollow and contain a notched body, and in a word, resem- 

 bles in every point the hollow lobes of fishes ; indeed, so strong is the 

 resemblance, that they have also before, a set of solid lobes, which arc 

 their olfactory lobes. 



A more plausible argument is drawn from the position of the pineal 

 gland. 



But in reality this part is not seen in a great number of fishes ; still 

 it would be difficult not to see in the eel, and especially the conger, a 

 small globular body of grey substance, placed anteriorly to the hollow 

 lobes and inserted into the posterior base of the solid lobes before 

 them by two small slips. 



In the cod and other fishes, where there is no globule, we can detect 

 at least, a small medullary thread floating in this place. 



If these parts represent the pineal gland and its pedicles, we shall 

 then be obliged to confess, no matter what system of analogy we 

 adopt, that there must be in the brain of fishes, at least, a transposi- 

 tion of connected parts. The third ventricle and infundibulum must 

 be flung into the back ground in the hypothesis, which represents the 

 hollow lobes as the analogues of the tubercula quadrigemina, and the 

 pineal gland must be brought forward in the hypothesis which consi- 

 ders these lobes as the hemispheres. 



With respect to the inferior lobes (e, e) since they manifestly give 

 out a portion of the fibres of the optic nerves, I considered them for- 

 merly as the analogues of the optic lobes in birds, which would have 

 descended still lower than the flying class ; but other anatomists pre- 

 fer the conclusion, that they are the analogues of the corpora albi- 

 cantia of man and other mammalia, eminences that are wanted in 

 birds and reptiles, and which, if this opinion were true, would abruptly 

 appear again in the fishes, and much larger in size than in the 

 mammalia. 



I must confess, that I am not a convert to the arguments in favour 

 of such allegations, and I have witnessed in the scale of living beings, 

 very little of those returns to life, of organs which suddenly spring up 

 in some single class, after having disappeared in one or two of those 

 above it in the scale. 



One peculiarity of the brain in fishes, not less remarkable than all 

 the preceding, consists in its lobes (g, g) being situated behind the 

 cerebellum on the sides of the fourth ventricle, forming frequently as 

 the cerebellum itself, a bridge across the ventricle. 



Their proportions vary very much, and the differences of their forms 

 and connections are numerous. 



In the rays and squalus, and even in the sturgeon, there are folds 

 or slips which prolong on each side the posterior edge of the base of 

 the cerebellum, and are supported behind in bordering the fourth 

 ventricle. 



In most fishes, they consist of two tubercles or projections from the 

 sides of the spinal marrow behind the cerebellum, which are touched 

 at some point, or are united by a commissure. 



In the cyprins, their volume is considerable, covering the whole of 

 this part of the spinol cord. Two small bosses are distinguished in 



