THE WONDER OF LIFE 555 



animals, the removal of the entire limb and shoulder girdle 

 of one side may still be followed by the re-growth of both 

 — ^which is an extraordinary instance of regenerative 

 capacity. 



In Linckia guildingii, a starfish common on the reefs of 

 Jamaica, the regenerative capacity is not less exuberant. 

 Dr. Hubert Lyman Clark observed that arms or rays 

 severed at some distance from the central disc give rise 

 to new discs and rays, just as well as those which separate 

 close to the disc. Rays are thrown off at irregular inter- 

 vals for a long period, if not throughout fife. In those 

 rays growth continues, especially at the broken end, where 

 new rays soon begin to appear, radiating out from a new 

 mouth. It seems, indeed, that in this case the giving off 

 of the rays and their subsequent regeneration of an entire 

 starfish must be regarded as an important mode of 

 asexual multiplication. 



Analogous Phenomena. — It is always a step towards 

 understanding to bring one kind of phenomenon into fine 

 with others. Thus it may be recalled that many of the 

 results of experimental embryology show that part of an 

 embryo has often the power of doing much more in the 

 way of development than is normally required of it. If 

 one of the first two cells into which the egg of a sea-urchin 

 or a lancelet divides be separated off, it may form a com- 

 plete embryo. A minute nucleated fragment of an egg 

 may develop into an embryo, which fives for a short time 

 at least. 



Secondly, we may recall the famifiar fact that in many 

 animals there is an almost continual process of tissue- 

 regeneration going on. Worn-out epidermic cells, glandular 

 cells, blood-corpuscles, and so forth are all replaced by 



