662 



Comparative Animal Physiology 



Numerous Ctenophora, perhaps all, are luminous. Here the light-produc- 

 ing cells are located along the meridional gastrovascular canals in the vicin- 



Connective f 

 strand 



Hypodermis 



Pigment laye 



ithelium 



Light cells 



Basement membrane 

 Reflecting layer 



Cuticle 



Light cells 



Mucous cells 



Fig. 251. A, Section through a Hght organ of the deep sea shrimp, Sergestes. From 

 Harvey.-' B, Section through Hght organ of the cephalopod, Romieletia. C, A section of 

 a luminous area of Chaetopterns epidermis. From Harvey,"^ after Dahlgren. 



ity of the germ cells. These organisms luminesce in resjxinse to stimuli, but 

 the response is inhibited bv bright light. After subjection to davlight the 



