ZOOL.— Vol. III.] BANCROFT— COMPOUND ASCIDIANS. 165 



place where there was an opportunity for it. In four cases 

 the isolated pieces of Woods Hole colonies were watched 

 carefully day by day, and the exact place of fusion noted. 

 Colonies which were well attached to a slide were taken, 

 the greater portion of them removed, and the pieces, sepa- 

 rated by intervals of a half or one centimeter, allowed to 

 grow towards each other. They were examined every day. 



In the first case, the fusion took place on the sixth, in the 

 second and third cases on the tenth, and in the last case on 

 the fifteenth day after the separation. 



In the first two cases, the isolated pieces developed at the 

 same rate ; so that at the time of fusion the zooids in both 

 pieces were in about the same phase. 



In the third case, embryos developed in both pieces, but 

 at different rates; so that, at the time of fusion, the larvae 

 had all been extruded in one piece, and the zooids which 

 contained them had entirely disappeared, while in the other 

 some of the old zooids with larvse remained. 



In the fourth case, embryos developed in only one of the 

 pieces, and its budding was retarded in consequence; so 

 that the change of zooids took place about a day after it had 

 been completed in the other piece. 



It is thus seen that in order that a fusion of two pieces of 

 one colony should take place, it is not necessary for the two 

 pieces to contain zooids of the same age or in the same 

 phase of development. 



3. Grafting in Botryllus and Botrylloides. 



After fusion had once been obtained between pieces of 

 the same colony, it was thought that although ordinarily 

 adjacent colonies would not fuse, still a union could be 

 obtained by means of grafting. This process was tried on 

 many colonies of Naples Botryllus, but was never success- 

 ful, even with colonies of the same color. In spite of 

 sewing and tying the colonies together, a vascular union 

 was never formed, though occasionally the tests of the two 

 colonies adhered slightly to one another. There seemed 



