366 WILLIAM H. COLE 



tion is slight. The abihty of the anterior edge of a piece of tail 

 of an amphibian to proliferate has been reported in the literature 

 several times. Vulpian ('59) observed a very slight proliferation 

 at the anterior ends of isolated tails of frog tadpoles. Later 

 Born ('97), by means of grafting experiments, demonstrated that 

 the anterior edge of tail pieces could produce new tissue. One 

 year later, Harrison ('98) observed proliferation in a tail which 

 had been grafted in reversed orientation. In other words, the 

 anterior end had proliferated tissue. In one case, where the tail 

 of one animal was grafted into the back region of another, the 

 anterior end proliferated more tissue than the posterior end. He 

 interprets this proliferation as an incomplete regeneration of a 

 body, rather than a heteromorphosis. 



In addition to polar proliferation, grafts showed also extremely 

 irregular outgrowths. Slender rods, curled or straight, thin 

 sheets growing out at different angles, bulbous and pocket forma- 

 tions are types of such irregular growths. Their distribution over 

 the surface of the graft was general, no area being exempt. 

 Several grafts which possessed outgrowths of all the kinds men- 

 tioned presented a grotesque appearance. One of the transplants 

 established union along its right side only, causing it to stand on 

 edge. Proliferation proceeded from both ends which turned 

 toward each other and fused, thus forming an open, hollow cone 

 4 mm. high. At this point growth ceased, the cone reniaining 

 unchanged for months afterward. There was exhibited in such 

 grafts, then, what may be called 'amorphic regeneration' (figs. 5, 

 7, 14). The size of the graft seemed to have no relation to the 

 rate or the amount of proliferation. Several times small irregular 

 masses of epidermis from the tail, less than 1 mm. across, were 

 transplanted to the back. All of them showed rapid proliferation, 

 until their size had been more than doubled in some cases. It is 

 suggested by this fact that the minimum size of a tail-skin trans- 

 plant which will proliferate is probably one active epidermal cell. 



Histological preparations of transplants which had proliferated 

 new tail tips at both ends showed that the notochord and the 

 nerve cord had been extended in both directions about four-fifths 

 of the length of the new tissue. Both of these structures appeared 



