1 68 RE GENERA TION 



which came from the minor component and appeared before the 

 aboral hydranth on the aboral end of the larger piece. This last 

 result shows that the small piece from the basal end has been affected 

 by the oral end in such a way that it develops more rapidly than it 

 would have done had it remained a part of the basal end. 



In a third series of experiments a short piece (about a half of a 

 millimetre) was cut from the anterior end of a long piece (one and 

 five-tenths to two centimetres) and grafted in a reversed position on 

 the posterior end of the same long piece (Fig. 49, G\ In four cases 

 a hydranth developed only at the oral end of the long piece and none 

 from the aboral end or from the short piece. Eight unions produced, 

 however, in the region of the graft, a hydranth formed partly by 

 each component. Later another hydranth developed at the oral end 

 of the larger piece. The latter results are not convincing, but they 

 may show that the small piece has hastened the development of the 

 hydranth at the aboral end. 



Peebles has also made some experiments in grafting pieces of dif- 

 ferent members of the colonies of hydractinia and podocoryne. The 

 colony of the former is made up of three different kinds of individ- 

 uals : the nutritive, the reproductive, and the protective hydroids. 

 A series of preliminary experiments showed that if these individuals 

 are cut into a number of pieces each piece regenerates the same kind 

 of individual as that of which it had been a part. It was also 

 observed that if pieces of the nutritive individuals were allowed to 

 remain quietly on the bottom of the dish they sent out branching 

 stolons, which stuck to the bottom of the dish, and from these stolons 

 there arose later nutritive hydranths that stood at right angles to the 

 surface. When pieces of the same kind of individuals are grafted 

 together, the results are essentially the same as with tubularia. If 

 pieces of different kinds of individuals are united, the opportunity 

 is given of testing the possible influence of one kind on the other. 

 Peebles united a nutritive and a protective polyp by the cut, aboral 

 ends (Fig. 46, E\ and after they had grown together one of the 

 polyps was cut off near the region of union, so that a small piece 

 of a nutritive polyp was left attached to a protective polyp. When 

 the piece of the nutritive polyp regenerated, it made a new nutritive 

 polyp. The influence of the protective polyp was not apparent. If 

 a nutritive and a reproductive polyp are united in the same way, and 

 the latter cut in two near the line of union, a new reproductive polyp 

 develops from the piece left attached to the nutritive polyp. Again 

 there is shown no influence of the one on the other kind of polyp. 



Hargitt has also made a number of grafting experiments on other 

 hydroids. His most interesting results are those in which parts of 

 two medusae were united by holding their cut-surfaces together by 



