228 C. W. Habu. 



not the case. It was found that in the monoglyphic polyps the 

 directive mesenteries arose regularly from the new or regenerated 

 portion of the body-wall, and that in the diglyphic polyps, likewise, 

 one of the two pairs of directives arose in this same position, but 

 the other arose from the old or parental tissue. This observa- 

 tion at once suggested a different explanation of the dimorphism, 

 viz: that it was due not to the monoglyphic or diglyphic nature 

 of the parent polyp, but to the character of the fragment from 

 which regeneration took place. If this fragment contained a 

 pair of directive mesenteries the polyp produced would be 

 diglyphic, since it would retain the pair of directives derived from 

 the parent and gain a second pair through regeneration. If, 

 on the other hand, the parent fragment contained no directive 

 mesenteries, then the regenerated polyp would be monoglyphic, 

 containing only the pair of directives produced in the new tissue. 



To test this hypothesis a more detailed examination of the 

 polyps was made, the monoglyphic polyps of different parentage 

 being compared with each other, and, likewise, the two lots of 

 diglyphic polyps with each other. 



In determining which is the regenerated portion of a polyp 

 no single character can be relied upon. Usually considerable 

 familiarity is necessary to enable one to distinguish regenerated 

 from parent tissue. The latter, as seen in cross-section, is usually 

 characterized by deep folds of the ectoderm into which small 

 V-shaped points of the mesoglcEa extend. (Figs, i and 2.) The 

 external surface in this side is more regular and evenly curved; 

 the mesenteries are quite regular, especially is this true of the 

 secondaries and tertiaries in relation to the primaries. The 

 primaries arising from the old portion of the body-wall are longer 

 than those arising from the regenerated part. The mesogloea 

 on the regenerated side is not of uniform thickness or contour 

 and does not conform as regularly with the folds of the ectoderm, 

 when such exist. Regenerated directives and old directives 

 usually differ in length and thickness when view^ed in cross- 

 sections, the former usually being short and thick. (Figs, i and 2.) 

 These conditions, however, vary greatly, but when the evidence 

 from one criterion is uncertain that furnished by other criteria is 

 usually conclusive. 



The results of the detailed examination made are incorporated 

 in Table II. From this it will be seen that the monoglyphic 



