552 



LIFE : OUTLINES OF GENERAL BIOLOGY 



(2) There may be some manipulation which secures the attach- 

 ment of the eggs and developing offspring to the parent. Thus some 

 mother-spiders fashion a silken bag or cocoon around the eggs and 

 attach this by threads to the under side of the body. 



(3) In other cases the care is expressed in hiding the eggs and 

 developing offspring. This may be a very simple matter, as when a 

 snail drops its egg'> into a hole in the ground, but it may have 

 considerable finesse, as when a sawfly bores a hole in wood and 

 deftly inserts an egg. 



(4) The hiding of the egg in a safe and suitable place often reaches 

 a high level of "instinctive art", which may require prolonged 

 manipulation. Thus the female trapdoor spiders make beautifully 

 finished shafts (furnished, for instance, with hinged lids) which are 

 shelters for the eggs and the young. Still more extraordinary is the 



Bunch of Sepia Kggs, attached 

 to a Shallow -water Marine 

 Plant. After Jatta. 



Fig. 86. 



Egg-clusters of the Squid 

 (Loligo), attached to a piece 

 of seaweed. 



silk nest which the Water Spider [Argyronela naians) spins in the 

 pool and fills with dry air. Its entire significance is in relation to the 

 eggs and the young spiders. 



(5) Another level is illustrated by those cases in which the mother 

 animal remains near the hidden eggs and developing offspring, and 

 may sometimes drive off intruders. Thus the Madagascar Crocodile 

 lingers beside the eggs laid in the soft ground, and Ls ready to 

 unearth the young ones when they are about to be hatched and pipe 

 from within the egg-shells. The male stickleback defends the weed- 

 nest which he has fashioned, in which the ab.sentee female parents 

 have deposited eggs. 



(6) Rising out of the protective lingering beside the developing 

 eggs are the various forms of brooding, which reaches its climax in 

 birds. This may secure not only safety, but a more rapid and smoother 

 development ; and it should be kept in mind that it is the rule with 

 migrant birds that they nest in the colder part of their migrational 



