220 DONALD WALTON DAVIS 



1101 diglyphic, 112 monoglyphic, 61 triglyphic, and 4 tetra- 

 glyph'c individuals. It will be understood that all stages of 

 regeneration were represented in specimens of these lots, and 

 that consequently many specimens in early stages of regeneration 

 failed to show siphonoglyphs that nevertheless would certainly 

 develop n the middle of the new region (p. 183). Such potential 

 siphonoglyphs were, of course, counted just as if they were 

 actually completed. 



Mesenteries 



No attempt has been made to determine directly the number 

 of mesenteries in numbers of individuals. Remembering the 

 relation shown to exist between mesenteries and orange stripes, 

 the counts of stripes presented hereafter have some significance 

 from this standpoint. Consideration has been given, however, 

 to the number of mesenteries of apparently undivided diglj^phic 

 specimens. Of the 1101 diglyphic individuals in the groups 

 represented in table 13, 63 failed to show in the living state 

 satisfactory signs of division. Forty-one of these were sec- 

 tioned and studied for internal evidences of division. Among 

 these, thirty gave unmistakable evidence of the sort already 

 described (pp. 169, 170), five showed slight irregularities such as 

 are commonly associated with fission and regeneration, while six 

 were forms without any irregularities to indicate unlike ages of 

 different parts. Of the six last mentioned specimens, five were 

 biradially symmetrical with six pairs of complete mesenteries, 

 and one had eight pairs. One with six pairs of complete mesen- 

 teries is represented in figure 26. Of the five slightly irregular 

 and therefore possibly undivided specimens, two possessed six 

 pairs of complete mesenteries, two had eight pairs, and one 

 showed ten, all being strictly biradially symmetrical. These 

 numbers are small, and their interpretation must be modified by 

 the fact that, among fully regenerated forms, regularly hexa- 

 meric individuals with twelve orange stripes (and by infer- 

 ence six pairs of complete mesenteries) are more numerous than 

 other forms. It can, at most, be said that, among apparently 

 undivided specimens, a regular form with six pairs of complete 

 mesenteries is the most common type. 



