218 DONALD WALTON DAVIS 



sector, there is ground for suspicion that not all of the orange 

 stripes of the 2one have appeared, or that a part of the regen- 

 erating region has been separated off in a later fission. As 

 previously stated (p. 167), there is danger, especially in faintly 

 colored specimens, of counting as an orange stripe the narrow 

 space representing the union of the torn edges shortly following 

 a division. This is especially likely in faintly colored indi- 

 viduals. It should be constantly guarded against when count- 

 ing stripes. When no slightly developed regenerating area is 

 present the internal structure may in most cases be accurately 

 inferred from the number of orange stripes. Thus Davenport's 

 ('03) figure 11 represents probably a specimen possessing material 

 of four different ages. The oldest shows three orange stripes; 

 the next oldest, two; the third, six, and the most recently formed 

 area, nine. All except the last formed sector have been partially 

 removed in the divisions which initiated the later regenerations. 

 If, in addition, the number and position of white bars on the oral 

 disc were known (thereby locating the directives), still other 

 details might be surmised. Under favorable conditions even the 

 incomplete mesenteries of second and later cycles may be 

 identified through the column wall after complete mesenteries 

 have been located. It should be clear, then, that careful exami- 

 nation of living specimens of S. luciae enables one to distinguish 

 recently divided specimens and to estimate approximately the 

 stage reached in the regenerating region; and, in specimens that 

 have not recently undergone fission, to infer quite accurately 

 and in detail the number, character, and positions of the 

 mesenteries. 



COMPOSITION OF NATURAL GROUPS 



We may now look into the composition of colonies of this 

 species and consider to what extent this composition is affected, 

 or accounted for, by the processes of asexual reproduction de- 

 scribed. This examination should also yield information con- 

 cerning the sexually produced form of the species. With these 

 questions in view, I have studied natural groups of individuals 

 taken at different seasons from a variety of situations around 

 Woods Hole. 



