REPRODUCTION 9 



the fullest extent among the lower animals. Here not only 

 small tracts of particular tissues can be renewed, but whole 

 parts of organs of the body. The most familiar example 

 is perhaps the well-known case of the lizard, which easily 

 re-grows its broken-off tail ; or of the triton, which will 

 replace a whole leg that has been lost. The crab has the 

 power of growing a new claw in place of that lost in a 

 fight with its rival, one kind actually snapping its own 

 leg when caught. The snail is able to renew its eye, to- 

 gether with the eye-bearing horn. Still lower in the scale, 

 we find the star-fish adding an arm that has been lost, or 

 the sea-cucumber its ejected viscera. 



(c) Artificial Division. 



But we are not yet at the end of the regenerative power 

 of Nature. Besides the accidental losses enumerated above, 

 which are easily made good again, we may go farther, and 

 actually divide some animals into several pieces without 

 any detriment to their existence. On the contrary, the 

 separated parts live on, re-create the missing parts, and 

 become fully-equipped individuals once more. Instead of 

 a loss of life, we have a multiple gain of it. 



Of these cases the most familiar example is the common 

 earthworm, which, when divided by the spade, grows into 

 two complete animals, each divided part regenerating the 

 missing portion of the body. The hydra-polypes, the sea- 

 anemones, the Planaria worm, may be cut into many 

 pieces, and each piece will grow again into a new com- 

 plete individual. To take cuttings and slips from plants 

 is a very common device of the gardener for multiplying his 

 stock. Even the smallest particle of a Begonia leaf will 

 grow into a complete plant again. 



We have thus reproduction of parts of the organism up 

 to any extent, the remaining cell-complex always making 

 up the missing part by vigorous multiplication. After all, 

 it is not more wonderful that the same cells which grew, let 



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