No. 6.] AMERICAN MORPHOLOGICAL SOCIETY. 355 



and large intestine. The collateral circulation to the large 

 intestine has apparently been established through the anterior 

 mesenteric artery; that to the ovaries, through vessels which 

 may have been formed as the result of a modification of the 

 posterior mesenteric artery. 



XX. SOME FACTS CONCERNING REGENERATION 

 AND REGULATION IN RENILLA. 



H. B. TORREY. 



DURING the past summer experiments were carried on at 

 Beaufort, North Carolina, preliminary to a more complete 

 investigation of the processes of regeneration and regulation 

 in Rcnilla. It was hoped that Rcnilla, being a polymorphic 

 colonial form, --an aggregate of polyps and zooids, -- would 

 behave like a simple metazoan individual, and at the same 

 time offer surer landmarks, during regulative processes, than 

 a metazoan individual --an aggregate of cells; for changes 

 in polyps as a whole may be perceived more clearly than 

 changes in their component cells. 



The results may be summarized as follows : 



1. Renilla colonies may regenerate lost parts readily. 



2. They exhibit a strong polarity. When a peduncle is 

 removed by a transverse cut an axial polyp is never regen- 

 erated in its place, and vice versa. 



3. There is an anterior limit beyond which anterior pieces 

 do not regenerate posteriorly, and a posterior limit beyond 

 which posterior pieces do not regenerate anteriorly. These 

 correspond to the limits of the budding zone. 



4. The colonies regulate themselves in a plastic fashion 

 when cut in certain ways, obliquely, for instance. It is thus 

 possible to obtain two new colonies, one of which retains the 

 original peduncle with a lateral polyp displaced into the posi- 

 tion formerly occupied by the axial polyp. Whether or not 

 the colony develops symmetrically around this new axis is 

 not known. 



