86 BULLETIN OF THE 



towards the side opposite the place of entrance, as the* fibres one after 

 another effected a union witli the basal ends of the retinal cells. But 

 nothing of the kind seems to exist in either of the cases cited or in those 

 which have come under my own observation. The fibres, instead of 

 following the surface of the bulb beneath the post-retinal membrane 

 (" sclera "), traverse directly the retinal layer in several groups.* Their 

 connection with the retinal cells, however, is not — as one Avould fairly 

 infer from Grenadier's account — at the posterior (originally free) ends, but 

 rather with the anterior parts of the cells, f — at least it may be designated 

 as certainly pre-nudear. + The evidence of this rests partly upon the 

 position and general direction of the nerve-strands in a region behind 

 the forming bacilli and in front of the nuclei, and partly on the modifi- 

 cation of form which many of the retinal cells and their nuclei exhibit 

 in consequence of this relation. The elongation of the anterior ends of 

 the nuclei § is so evidently a result of the peculiar position and connec- 

 tions of the nerve-filaments (PL V, Figs. 23, 24) that I cannot for a 

 moment think it attributable to any other cause. 



There is also reason to believe that a similar condition exists in the 

 eyes of the " post-nuclear " type, and that the nerve-fibres which appear 

 to emerge from the deep surface of the retinal layer really pass around 

 the margins of the tapetum (somewhat as in Pecten), to join the now super- 

 ficial ends of the retinal cells This in turn increases the probability of 

 the inversion of the retina in " post-nuclear" eyes. (Compare Explanation 

 of Figures.) 



I shall return to a consideration of the manner in whicli this interest- 

 ing connection is brought about in the pre-nuclear eyes, and of the prob- 



* Since the groups do not necessarily lie in the plane of the section, they are not 

 all seen in one section ; but I am satisfied, from the examination of several cases, that 

 such a division of the fibres usually takes place. 



t That such a method of nerve-connection with sensory cells is not wholly with- 

 out parallel, will be evident upon comparing tlie conditions here described with the 

 account of the termination of the radial nerve of the cochlea in mammals as given 

 by Lavdowsky (76, pp. 529, 530, Taf. 35, Figg. 10 A, 10 C). 



X The connection here (after inversion) called "pre-nuclear" is of course equiva- 

 lent to a post-nuclear connection before inversion. The nerve-fibre, which I believe 

 I'eaches the nucleus itself, therefore retains as nearly as possible its original method 

 of connection with the retinal cells ; i. e., it approaches the nucleus from what was 

 originally the deep end of the hypodermal cell. 



§ The nuclei present no such modification of form in the earlier stages of tlie 

 formation of the eye, before the appearance of the optic nerve, but are sinalarlv 

 rounded at both ends. 



