NOTES ON THE PHOTOPHORES OF SERGESTES PREHENSILIS BATE. 309 



easily be overlooked, as indeed Kemp seems to have done in the photo- 

 genous cells of ^. challenger i. 



The body of the photogenous cells, fixed with Flemming's fluid or 

 with picric acid mixtures, is densely and uniformly fine-granular. This 

 condition I regard to fairly represent the normal. The granules are 

 moderately refractive. In the material treated with Flemming's fluid and 

 stained with safranin, the cell-body appears rosy red. Using picric 

 acid fixatives, fuchsin stains it red, Freeborn's picro-nigrosin yellow, 

 Heidenhain's iron-haematoxylin blackish, and Congo red yellowish. It 

 shows strong affinity towards eosin but very slightly towards Delafield's 

 haematoxylin. 



According to Kemp, there exist deep blue pigments in the photogenous 

 cells of 5". challengeri. It is noteworthy that I have found nothing like 

 them in the same cells of 6". prehensilis, in both the fresh and the fixed 

 state. 



As before indicated, there exists, marginally to the photogenous layer 

 and directly beneath the lens epithelium in the periphery of the inner lens 

 surface, a zone which is entirely devoid of the photogenous cells and 

 consists of a haemal space traversed by some thin fibres, in much the same 

 manner as the haemal spaces between photogenous cells are by the con- 

 nective strands. I believe that the said fibres and the connective strands 

 are in fact identical structures derived from the cells of the lens epithelium, 

 and that the marginal zone in question is genetically the same as the more 

 centrally situated photogenous layer, but has not given rise to photogenous 

 cells, which probably also originate from certain cells of the lens epithelium 

 by special development. Kemp has entered, in his semi-diagrammatic 

 figures (op. cit., pl. LIV< figs. 2, 3, 5), some small cells in the marginal 

 parts of the photogenous layer, although none of the photographs given by 

 him (pl. LIII, figs. 2—4) clearly shows the same cells. If the cells in ques- 

 tion do really exist", they may perhaps be interpreted as representing the 



* Possibly the bodies here referred to as cells are not cells at all, but disintegration products 

 of photogenous cells. 



