CENTRAL NERVOUS SYSTEM IN VERTEBRATE ANIMALS. 
953 
tribution. These Fishes certainly have organs placed along the side near the tail, 
which by some writers have been looked upon as electric lobes, and which, although 
presenting some of the structure of those bodies, yet show that they are pseudo¬ 
electric organs, since they give no shocks when the'Fish is handled. This fact, however, 
seems to have no connexion with the development of the brain, for the lateral line and 
dorsal nerves which supply those structures are by no means of enormous size. This 
subject must therefore remain in obscurity until some competent person may be in a 
position to throw light on it by means of physiological experiments, to which the 
formation of the brain lends itself with great facility, because it is placed close beneath 
the skull, which is very thin, and the wings form plates of nervous matter easily 
removable without injury to other parts of the organ. 
Conclusion. 
Although the brain of the Mormyriclw, being squeezed almost out of all recognition, 
does not throw much light on the problem of the homologies of the various parts of the 
central nervous system in Fishes, yet I must take this opportunity of making some 
remarks on the interpretations put forward by Fritsch'" in his great work, which I 
had not time to study before my paper on the brain of the Teleostei was finished. As far 
as I can make out from his rather involved style, he considers that the tecta lobi opticit 
taken together represent the persistent cortex of the primitive anterior vesicle of the 
embryo ;J nevertheless, he recognises in the commissure of the tecta the homologue of 
the corpus callosum§ and in the torus longitudinalis that of the fornix of the Mam¬ 
malian brain. Both these structures are developed from what Fritsch terms the 
secondary vesicles, || from which the cerebral hemispheres arise. How they get trans¬ 
ferred to the primary vesicle this author does not explain. Further, he homologises 
the tori semicirculares with the thalami optici, and certain undefined regions lying 
to the inside of them with the corpora quadrigemina. 
It seems to me that there are two fixed points in the brain of Fishes from which it 
wmuld be possible to deduce the homologies of all the remainder. The first of these is the 
pineal gland or epiphysis, together with the infundibulum, which opens beneath it, and 
the pituitary body or hypophysis which is placed at the inferior extremity of the latter. 
EhlersH has shown that the epiphysis is a structure universally present in the Verte- 
brata, and that it invariably occupies a corresponding position throughout. The proba¬ 
bility is that the infundibulum is a channel older even than the Vertebrate stock itself ; 
and in reference to this subject perhaps I might be permitted to express my gratification 
* Log. cit. 
t Loc. cit., pp. 22 and 54. 
t Primares Vorderhirn. 
§ Loc. cit., p. 51, fig. 42. 
|| “ Secundares Vorderhirn.” 
*|[ Die Epipliyse am Gehirn d. Plagiostomen. ZeitscTi. f. wiss. Zoologie, Bd. 30 (supplement), 18/8. 
6 F 2 
