264 OF THE DEEP-SEA CRUSTACEA 



is a burrowing crustacean, degeneration has gone one 

 stage further. Here the eyes are barely distinguish- 

 able from the short and slender eye-stalks, and may 

 truly be said to be useless rudiments. Forlorn eye- 

 stalks of the same kind are all that remain to Phobertts 

 ccems, a large spiny lobster, from 500-1000 fathoms, 

 and to the scissor-foot prawn Psalidopus (Fig. 21), 

 from 400-600 fathoms, as well as to certain deep-sea 

 crabs that might be mentioned. The figure of 

 Nephropsis (Fig. 59), which represents a male, shows 

 the thickened outer or olfactory branch of the first 

 pair of antennae, the greater development of the organ 

 of smell being probably a compensation for defective 

 eyesight. 



The final stage of degeneration, in which the 

 eyes have altogether disappeared, leaving only the 

 bare ruins of an eye-stalk behind them, is well illus- 

 trated by the blind shrimp, Prionoc7^angon ommatosteres 

 (Fig. 20), whose eye-stalks are represented by a pair 

 of useless scales. Similiar useless but eloquent eye- 

 stalks are to be seen in a blind scorpion-lobster 

 (Callianassa ccecigena), from 200-350 fathoms, and in 

 a blind Schizopod [Petalophthalmus ai'miger), from 902 

 fathoms. In all the recent Eryonidce, too, of which 

 Pentacheles hextii (Fig. 60), from 188-719 fathoms, is 

 a good example, the eye-stalks, bereft of eyes, are 

 firmly adherent to the carapace, a condition which is 

 the next stage to complete disappearance. 



