164 CALIFORNIA ACADEMY OF SCIENCES. [Proc 3D Ser. 



two zooids are enclosed in a common test, two notches only- 

 remaining to indicate the former line of separation. Certain 

 of the blood-vessels have also fused, forming a single 

 vascular system for the two zooids. 



The writer's investigations on this subject were completed 

 about eight months before the publication of the paper of 

 Pizon, above referred to, and were performed with unrelated 

 adult colonies, with pieces of the same colony, with unre- 

 lated, and sister and brother embryozooids, and with the 

 adult colonies developed from these related embryozooids. 



I. Fusion in Unrelated Adult Colonies. 



The fact that ordinarily colonies do not fuse with one 

 another is satisfactorily demonstrated by a mere inspection 

 of any lot of colonies, especially such a lot as may be 

 obtained from the Eel-pond at Woods Hole. At this place 

 the writer has examined hundreds of pairs of colonies that 

 were closely pressed against each other, but has never seen 

 any evidence of fusing. The colonies are everywhere dis- 

 tinct, and their zooids always of the same color. At 

 Naples, as already stated, zooids of different colors have 

 been seen in the same colony; but this difference is not 

 due to the fusion of colonies. It may be confidently stated, 

 then, that: In general, unrelated colonies, such as are found 

 next to each other in nature, do not fuse, but struggle with 

 each other for a substratum to grozu upon. 



2. Fusion between Isolated Pieces of the 

 Same Colony. 



If a colony is cut into several pieces, the wounds heal in 

 a few minutes. In a day such pieces cannot be distinguished 

 from ordinary colonies. If now these pieces are allowed to 

 grow naturally toward each other, they will not compete, but 

 fuse completely, both test and vessels of one piece becoming 

 united with the same organs in the other. This fusion was 

 observed very many times, and in no case did it fail to take 



