ASEXUAL REPRODUCTION IN SAGARTIA 175 



mesentery, and one part lacking directives. One of the tri- 

 glyphic animals (no. 10) divided in a directive endocoel on one 

 side, each of the two resulting individuals receiving a pair of 

 directives and an unpaired directive (in one part the directive 

 on the boundary being absent). A second triglyphic specimen 

 (no. 22) divided into three parts, one receiving a pair of directives, 

 another receiving a single directive mesentery on one boundary, 

 and the third receiving a pair of directives and an unpaired 

 directive. The third triglyphic animal (no. 20) divided into 

 three parts. One part received one pair of directives; a second 

 part possessed no old directives, and the third, which was not 

 successfully preserved, must have received two pairs of directive 

 mesenteries. The monoglyphic animal (no. 18) divided into 

 three parts not through the directive endocoel. Consequently 

 one part possesses a pair of old directives and two parts have 

 none. The tetraglyphic specimen (no. 15) divided into two, 

 giving one part three pairs of directives, the other one pair. 



Thus in fifteen out of seventeen cases of the division of di- 

 glyphic individuals the plane or planes of division cut the major 

 transverse axis, giving the pair of directives at the extremities of 

 this axis to different pieces. The division of the monoglyphic 

 specimen occurred in a corresponding plane. One of the 

 triglyphic specimens divided along a similar plane as regards 

 two of its pairs of directives, the division passing through the third 

 directive endocoel. In three of the four remaining cases (nos. 16, 

 21, and 22) some of the directives are regenerated ones whose 

 imperfective development at the time of division may give 

 occasion for the unusual position of the fission plane. The 

 fourth specimen (no. 15) also has some regenerated mesenteries, 

 but the limits of the regenerating zones are obscure, owing, at 

 least in part, to faulty preservation and to sectioning in a some- 

 what oblique plane. What part the directives play in de- 

 termining the position of the division plane may only be sur- 

 mised. This question is discussed below. Here it should be 

 emphasized, first, that the number of directives does not de- 

 termine the number of parts into which a polyp shall divide; 

 secondly, that in division there may be separated a piece which 



