WEISMANN*S THEORY OF THE GERMPLASM 73 



green hydra, Hydra viridis, upon the common 

 hydra. 



Transplantations of single tissues or organs have 

 been made more often, and by several investigators. 

 I shall mention only the older results of Oilier and 

 M. Bert, and those made in 1893 by A. Schmitt and 

 Beresowsky. 



Oilier exposed the bone of an animal, and, care- 

 fully removing a part of the periosteum, planted it 

 in the connective tissue under the skin in another 

 part of the body. The consequences differed 

 according as the transplanted tissue was imbedded 

 in another animal of the same species, or of another 

 species. In the first case the piece of periosteum 

 grew, obtaining a supply of blood from vessels 

 which grew out into it from the surrounding con- 

 nective tissue in which it was embedded. In a 

 short time lamellae of bone were formed by the 

 layer of osteoblasts, so that a small plate of bone 

 was formed under the skin. This, however, proved 

 always but a temporary structure, for, being formed 

 in an inappropriate spot, and, therefore, being 

 functionless, it was soon reabsorbed. In the second 

 case, however, in which the piece of periosteum 

 was removed from the bone of a dog and planted 

 in a cat, rabbit, goat, camel, or fowl (or vice versa), 

 formation of bone did not occur ; either the piece 



7 0. 



of periosteum was absorbed, or set up suppuration 

 around it, or became enclosed in a cyst. 



Paul Bert's experiments were the following. He 

 removed pieces two or three centimetres long from 

 the tails of white rats a few days old, skinned each 



