226 DONALD WALTON DAVIS 



directives varies from five to twelve. Three or four grades of 

 incomplete mesenteries may be found (p. 164 and tables 11 and 13). 



Asexual reproduction in this species occurs by a process of 

 aboral-oral fission with subsequent regeneration (p. 167). In 

 this process movements of parts of the basal disc in opposite 

 directions are initiated, centering in two or more isolated re- 

 gions. These movements place the intervening tissues of the 

 base under strain and result in a rupture of the basal wall. 

 The rent progresses until base, column and esophagus are suc- 

 cessively involved, and complete separation of the individual 

 into two or more pieces finally results. 



Details are recorded of the divisions of one monoglyphic, one 

 tetraglyphic, three triglyphic, and seventeen diglyphic speci- 

 mens (p. 174 and tables 3 to 5). 



The resulting pieces may possess one or more siphonoglyphs 

 and associated pairs of directive mesenteries or they may lack 

 these structures until regeneration has occurred (pp. 174, 175). 



Succeeding divisions may be delayed until regeneration is 

 completed or they may occur at any earlier time. They may 

 even follow so rapidly as to give the appearance of simultaneous 

 division into more than two pieces. In every such case a re- 

 generation zone is formed in each piece for each successive 

 fission (p. 173). 



In passing upward the plane of fission rarely cuts a mesentery, 

 i.e., the plane is a strictly vertical one (p. 171). 



There is no tendency toward strict equality of the products of 

 a division (p. 181). 



Strictly diradially symmetrical polyps tend to divide into parts 

 which are themselves symmetrical with respect to the original 

 directive plane, i.e., the plane of division tends to be approxi- 

 mately perpendicular to the major axis of the mouth (p. 176), 

 but no tendency to divide in spaces of the same kind on opposite 

 sides of the column was detected (p. 177). 



While division may occur in any vertical plane, it tends to 

 occur in endocoels rather than exocoels (p. 179), in complete 

 endocoels rather than incomplete endocoels (p. 180), and in 

 non-directive rather than directive complete endocoels (p. 180). 



