396 



on both sides as far as the cranial walls, but its connection with 

 the optic lobes was not ascertained. A few muscular fibres were 

 seen in contact with each eye dot, but there was no insertion into 

 it, as they all passed beyond it. 



Under the microscope the eye dot was seen to consist of a thin, 

 external sheath, continuous with that which covered the nerve. 

 Within the sheath was a layer of pigment cells, of hexagonal 

 form, investing the whole organ, and darkest at the two poles. 

 No opening for the admission of light was seen ; but, in two 

 instances, there was visible either near the anterior part of the 

 eye dot, or even connected with it, a lenticular shaped body, 

 consisting of an external membrane, including cells, the nuclei 

 of which were conspicuous. 



Morphologically considered, the eye dot, with its nerve, appears 

 to represent that portion of the organ of vision which is developed 

 in connection with the nervous centres. The external sheath, 

 though very thin, may represent the sclerotic coat, and the pig- 

 ment layer the choroid. Having no connection with the skin, 

 we should not expect to find those parts, among them the crystal- 

 line lens, which are in other animals developed by a folding in of 

 the integument, yet .a lens appears to exist. 



Prof. Owen regards the eye of the Amblyopsis as a modified 

 cutaneous follicle, but in the specimen just described, it was 

 wholly independent of the skin. 



There is nothing in the structure of the eye of Amblyopsis 

 which would lead to the supposition that it could assist in forming 

 a distinct image. The nervous filament, if it entered the interior 

 of the eye, would be protected by the pigment from being acted 

 upon by light. 



Dr. Cabot stated that on approaching the water in which 

 these fish are contained, they do not appear aware of any 

 change in light or darkness ; but, on touching the water, 

 they immediately retreat in the opposite direction. 



Prof. Wyman said the whole head was presumed to be 

 remarkably sensitive, it being covered with papillae, sup- 



