130 THE LIFE OF CRUSTACEA 



gut, or by infolding of its walls, in animals that have 

 to swallow large quantities of relatively innutritious 

 food material. Many species, however, no doubt 

 have more selective habits of feeding. The lobster- 

 like Thaumastocheles (Fig. 44), which was dredged by 

 the Challenger expedition in the West Indies at a 

 depth of 450 fathoms, and has since been got from 

 deep water off the Japanese coast, has one of the 

 chelae enormously enlarged, with long and slender 

 fingers set with spines like the teeth of a rake. It 

 has been suggested that this remarkable claw may 

 be used for raking or sifting the ooze for small 

 animals on which the Thaumastocheles feeds. A 

 similar function may be suggested for the long and 

 spiny first pair of walking legs in the Spider Crab 

 Platymaia (Fig. 45). 



In many deep-sea Crustacea the eggs are of very 

 large size, indicating that the young are hatched in 

 an advanced stage of development. For example, 

 in the numerous species of the genus Munidopsis the 

 eggs are always large and correspondingly few in 

 number, in striking contrast to the closely allied 

 genus Galathea, from shallow water, in which the 

 eggs are small and very numerous. Alcock mentions 

 that a deep-sea Prawn of the genus Psathyrocaris, 

 although only about 3J inches long, has eggs nearly 

 a quarter of an inch in length. It would seem that, 

 in some way or other, the conditions are unfavour- 

 able for a free-swimming larval life ; but they cannot 



