136 



HISTOLOGY 



some shrinking, and the artificial separation of some of the cells is 

 reproduced in Figure 123 at art. 



The two or three large cells, which lie above this central layer and 

 usually also directly above one another, are specialized to form in their 

 cytoplasm very large, solid concretions which may act as a lens to con- 

 centrate the light as it passes out. The outer of these cells are the larger, 

 and have the concretion developed in size almost to the point that a fat 

 globule is sometimes developed in its cell. In the inner cell the concre- 



FIG. 124. Section of light-organ of a deep-sea fish, Gigantactus. lum.ep., luminous epithe- 

 lium; ref., reflector; pg., pigment layer; dt., duct with enlarged chamber. (After A. 

 BRAUER.) 



tion is evidently in an earlier stage of development, and that brings up the 

 question as to whether the light cells or the lens cells are renewed by 

 growth processes or not. Their origin from a stratified epithelium would 

 lead one to think that they were constantly worn out and replaced, 

 while the position of the lens cells would suggest that the latter must 

 remain where they are unless they go through a stage in which they 

 are light cells and are finally thrown off. There is probably no renewal. 

 A regeneration, in case of such abrasion as must often occur, is pos- 

 sible. 



