154 



THE LIFE OF CRUSTACEA 



lengthened and with reduced pigment, while the 

 lateral part is of more normal structure. It seems 

 probable, from the researches of Professor Chun, 

 that the fronto-dorsal division is adapted for the 

 perception of very faint light, while the lateral 

 division will give a more accurate image of brightly 

 illuminated objects. 



Fig. 54 — Phronitna colletti, Male. From a Specimen taken in Deep 

 Water near the Canary Islands, x 12. (After Chun.) 



In the pelagic Amphipoda, forming the suborder 

 Hyperiidea, the eyes are of very large size, generally 

 occupying almost the whole surface of the head, and 

 giving the animals a very characteristic appear- 

 ance, in contrast to the small-eyed, bottom-living 

 Gammaridea. In the family Phronimidae (Fig. 54) 

 the eyes are each divided into two parts, differing in 

 structure in the way just described. 



