CH. IV] LIFE IN THE SEA 93 



fish hatches out fi:-om the egg it is already a large and predatory 

 creature which is able to seek shelter and to find food. The vivi- 

 parous dogfishes have even greater advantages. The young, because 

 of their mode of development, escape the dangers of embryonic and 

 larval life and when they are born are active creatures which are 

 able to avoid some at least of their enemies. The intelligent and 

 pugnacious lobster carries its eggs attached to the abdominal feet, 

 and during the nine or ten months required for the incubation 

 of these they are immune from enemies. Even the fisherman is 

 prohibited by law from taking the nursing lobster or crab. 

 Generally among the Crustacea the eggs are carried by the mother 

 during the incubatory period, and there are hosts of devices by 

 which these, and other marine animals, are enabled to carry and 

 protect their eggs and larvae : such are brood-pouches and chambers, 

 egg-sacs, &c. Some of the fishes devote what we must call pur- 

 poseful and intelligent care to the fostering of the eggs and young. 

 The male pipe-fish carries the eggs in a brood-pouch ; the lump- 

 sucker guards the mass of ova laid by the female, and keeps it 

 aerated by blowing water upon it fi'om his mouth, or by waving his 

 tail backwards and forwards in front of the egg heap. Often his 

 devotion is the cause of his death, for the eggs may be deposited 

 in a rockpool which may be exposed by a spring tide and the 

 unhappy parent may then be attacked by predatory birds or small 

 boys. The fifteen-spined stickleback builds a nest out of sea- weeds 

 and cements these together by a viscid fluid secreted by him at the 

 spawning time. In this nest are laid the eggs of one or more 

 females. And so all through the marine fauna. Fully to relate 

 the methods developed by natural selection for the protection of 

 the eggs and young stages of fishes and other marine animals 

 would require a large volume. 



Now we may return to the plankton. We have seen that this 

 contains both permanent and transitory components. Hosts of 

 benthic animals and plants while they are still in the larval, or 

 sporing phases, live among the drifting microscopic life of the sea 

 and then disappear, having assumed some one of the other modes 

 of life. If then we consider only the transitory life of the plankton 

 we should expect to find that both the nature and amount of the 

 organisms present should vary with the season, and observation 



