Biology 691 



7 

 Remarkable Experiments 



Other such apparent miracles, depending upon the reorgan- 

 ising power of living things, are seen as the result of grafting 

 experiments. It is comparatively easy to graft pieces of earth- 

 worms together, and by this means worms have been produced 

 longer than normal; shorter than normal; with a central piece 

 reversed so that its front end points to the rear; and all appar- 

 ently healthy. But this pales before the remarkable experiment 

 of Harrison, who grafted the front half of a newly hatched tad- 

 pole of one species on to the posterior half of the tadpole of 

 another species. The compound creature throve, grew, and meta- 

 morphosed into a normal frog. The only unusual point about it 

 was the fact that, since the two species of frog differed in colour, 

 one-half of the animal was light-coloured, the other dark. 



In plants, even more intimate unions have been made. 

 Winkler grafted a piece of one species of Solanum (the genus 

 to which the potato belongs) on to a stock of another species, 

 waited until the union had been well-established, and then cut 

 the stem across, just at the point of junction. The bud which 

 grew out was formed of the intermingled tissues of the two 

 species, the outer layers being formed from one, the inner from 

 the other. It was a real example of "being in someone else's 

 skin." The compound plant, or graft -hybrid, was healthy, the 

 only sign of abnormality being that, since the rates of growth 

 of the two components were not quite the same, the skin did not 

 fit accurately over the core and the leaves had a crinkled look. 



As we ascend the scale of animal life, the power of regenera- 

 tion dwindles. A crab or a newt will die if it is cut in two, but it 

 retains the power of restoring lost limbs. It is at first sight very 

 remarkable that the animal can restore just what was lost, no less 

 and no more, but this becomes more intelligible if we think in terms 

 of the idea of equilibrium. The balance is upset by the operation, 

 and it is not restored until the missing part has been replaced. 



