250 STALK-EYED CRUSTACEA. 
may well be that after these types had become acclimated to the depths, 
their young still found in the ancestral surface life the conditions most favor- 
able for their development. The toad still goes to the water to spawn, the 
land-crab goes to the sea, The journey of a swimming prawn from a depth 
of 1000 fathoms or more to the surface to spawn does not impress one as 
more remarkable than the periodic passage of anadromous fishes from the 
sea to fresh waters in their solicitude for the welfare of their young. The 
advantage gained for the race, too, through the wide dispersal of pelagic 
larvee by the ocean currents is obvious. 
Most of the Stalk-eyed Crustacea, as is well known, protect their eggs 
for a longer or shorter period after they are laid, either carrying them under 
the tail, or, as in the Schizopoda, brooding them in a special pouch beneath 
the breast. In many of the deep-sea species the eggs attain an enormous 
size before they hatch. From analogy with certain land and fresh-water 
species, we infer that in these cases the young quits the egg, or, which is the 
same thing, leaves the mother in an advanced stage of development, ready 
to lead a life similar to that of its parents. But it is a remarkable fact that 
none of the deep-sea swimming forms belonging to the family Peneidx are 
ever found carrying their eggs. The natural inference from this is that the 
young must be quickly hatched, in a very immature state, best fitted for sur- 
face life, like the larvee of the littoral species belonging to the same family. 
This certainly adds weight to Spence Bate’s suggestion concerning the occa- 
sional occurrence of such forms at the surface. It is also worthy of note in 
this connection, that Acanthephyra agassizii, one of the Hoplophoridx that 
has been taken at the surface, has eggs of normal size. 
bas 
