24 



THE PINEAL ORGAN 



to such eyes as those of vertebrates and some molluscs and chaetopods. 

 The pair of similar organs behind the two composite faceted eyes 

 apparently escaped Claus's notice. Vallentin and Cunningham record 

 that the light which is given off in " flashes " in response to stimulation 

 is always intermittent in character, not continuous as in some " phos- 

 phorescent " organs, and they showed that the parts of the organ from 

 which the light was emitted was the reflector (Fig. 18). 



Fig. 18. — Section of the Photospherion of the first Abdominal Somite of 

 Nyctiphanes Norwegica. (After Vallentin and Cunningham.) 



Two possible ways of obtaining a composite eye from ocelli suggest 

 themselves : (i) groups of separate ocelli may fuse to form a composite 

 organ ; or (2) the individual cells composing an ocellus may divide in 

 such a way as to form groups of cells lying side by side. 



The latter process has been shown to occur by Kingsley 1 in the 

 development of the stalked eyes of Crangon (shrimp), and this has been 



1 J. S. Kingsley (1886), Zool. Anz., 9, 597. 



