YOUNG SUCKING NELSONS. 125 



that the hermit-crab has been trying to say good-bye for 

 ever to the sea for so many ages (and so far as his adult 

 hfe is concerned has been successful), these arrangements 

 for his delicate progeny have so far fallen short of perfec- 

 tion that they are still dependent upon salt water ; and 

 after being hatched on shore must needs return to their 

 old dominion, there to go through the various stages of 

 growth which characterise their juvenile existence. 



There are doubtless many people who are under the 

 impression that when the eggs of a crustacean (water- 

 fleas, barnacles, shrimps, lobsters, crabs, etc.) are hatched,, 

 a diminutive crustacean, identical in structure and habits 

 with its infinitely larger parent, at once appears in the 

 world. Such, however, is very far from being the usual 

 case. Some Crustacea, it is true, have become so highly 

 developed or modified that they have been successful 

 in this respect ; so that in transferring themselves from 

 the sea to land or fresh water, the various larval stages 

 of existence (Nauplius ; Zooea ; Megalopa) through which 

 ordinai^ily the young crustacean passes, have been sup- 

 pressed, or rather hurried through in the egg, before the 

 latter is hatched. The cray-fishes, for instance, have so 

 succeeded. So has the ditch-prawn (Palcemonetes), and 

 we might also mention the case of the river-crabs 

 (Potamonetes). In all these forms the eggs hatch directly 

 into the adult form. But the adult land hermit-crabs, 

 land-lubbers as they have become in these days, have still 

 to send their young to sea, where for a time they fend and 

 shift for themselves, as the old sea-dogs did themselves. 

 For some time, the eggs are carried about on shore, snugly 

 hidden away in the shell which the female crab inhabits, 

 and attached in large masses to the long hairs, growing 

 on the well-developed limbs on the right side of the 

 second, third and fourth abdominal segments of her 

 body. After a certain period, not definitely known, 

 the mother crab repairs to the sea-shore ; and her© 

 probably, while she crawls about on the wet sand, or 

 clings to the rocks on the tide-line, the salt water gains 



