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THE EVOLUTION OF SEX. 



offspring. Even in some coelenterates, worms, and echinoderms, the 

 offspring cling about the mother animals, and may be protected in 

 various kinds of brood-chambers. In some lowly crustaceans, the 

 young may return to the shell-cavity of the mother after hatching, and 

 even after they have undergone a moulting. The young crayfish are 

 said to return to the maternal shelter after they have been set adrift. 

 The care of the nurse-bees for their charge, though not exactly 

 maternal, deserves to be recalled; and the way in which ants save 



FlG. 07. — A Male "Seaspider," or Pycnogonid, carrying the ova. — 

 After Carus Sterne. 



the cocoons when danger threatens is well known. De Geer describes 

 how one of the insects infesting plants behaves to her young brood 

 exactly like a hen with her chickens; and Bonnet vividly describes a 

 case where a mother spider, at the mercy of an ant-lion, fought for 

 her eggs at the sacrifice of her own life. Some spiders, too, carry 

 their young; and some crustaceans, like Gammarus, swim along with 

 their young ones, like a hen among her chickens. Some cuttlefishes 

 take pains in keeping their egg-clusters clean and safe; while even 

 the headless fresh-water mussel retains her young, when there is no 



