259 



eye, by appealing to the observations ofKingsley, who, he claims, 

 has actually seen the intrusion of mesodermic tissue into the eye. 

 We find, on consulting Kingsley's short paper of about three pages, 

 that he has described nothing of the kind, but clearly shows that the 

 ommateal pigment is ofectoderraic origin. We surely should expect 

 that Prof. Lankester, who in language more forcible than courteous 

 speaks of my »incapacity for accurate observation of books« and of 

 »recklessly attributing to other authorities statements which are the 

 reverse of those made by the gentlemen in question«, would at least 

 avoid those errors which he criticises so severely in others. 



7) On p. 289, Prof. Lankester states that one of the most im- 

 portant lines of inquiry into the minute study of Invertebrate eyes is 

 to be found in a determination of the distribution of pigment in the 

 retinal cells, and adds that »Dr. Patten has not given as much atten- 

 tion to this matter as we could wish. It is remarkable that while he in- 

 dulges in such ,tall talk' about pigment and heliophagy he professes 

 to have traced the chief optic nerve fibres of Arthropod eyes to the 

 colorless cells«. The reader will be surprised to learn that the question 

 of the presence of pigment in the retinal cells of Molluscs was the 

 theme of my study upon the Molluscan eyes, and the one which fur- 

 nished me with the most important results of my paper. Prof. Lan- 

 kester would not have considered it »remarkable« that the »nerve- 

 end« cells of the Arthropod eye were col orless, if he had taken pains 

 to read that part of my paper devoted to Molluscs. I have shown that 

 in the simplest Molluscan eyes most of the retinal cells, if not all, were 

 pigmented, while in the higher forms the true sensitive elements were 

 colorless ; therefore the presence of colorless »nerve-end« cells in the 

 Arthropod eye is exactly what we should expect. I, moreover, explained 

 at length, and illustrated by numerous diagrams, the various 

 steps in the phylogenetic development of the colorless cells and the 

 degeneration of the pigmented ones, throughout the Molluscan and 

 Arthropod groups. 



8) Prof. Lankester, Avhile commenting upon my observations of 

 intercellular nerves in Molluscs, asserts the well known fact that such 

 nerves have also been observed in Vertebrates. But, he adds, as though 

 it were in conflict with my observations, it is also very generally held 

 that, in organs of special sense, the nerve fibres terminate in the sub- 

 stance of special nerve-end cells. It is a sufficient comment on Prof. 

 Lankester's criticism, that I have repeatedly regarded the presence 

 of such intra-cellular nerve fibres as a criterion in determining what 

 .the special sense cells of the eyes were. 



9) On p. 286, my assertion that nerves end between the cells in 



