398 TORREY 



in diglyphic polyps, in exceptional cases, both or neither may be in- 

 volved. In such cases the plane of division may be perpendicular to 

 or parallel with the major axis of the mouth. 



Budding takes place either (a) in the cesophageal region, where the 

 oesophagus of the bud may or may not be independent of that of the 

 parent, and the buds may vary greatly in size; or (6) in the vicinity 

 of the foot disk, where the buds are relatively very small. 



It has been shown by Pai^ker that fission of the typical sort may be 

 complete ; so that the partially separated individuals commonly found 

 are not monsters, but represent stages in the process. The progress of 

 division, however, is extremely slow, requiring many months at least 

 for its completion. Whether cesophageal buds ever become free is not 

 known, so far as I am aware, although buds from near the foot disk 

 may detach themselves in a few weeks. 



That neither fission nor budding has more than a trifling influence 

 on the number of individuals will be apparent from the following fig- 

 ures. Among 2,662 polyps observed, only 67, or 2.5 percent, were 

 monogenous. Among 46 of these monogenous polyps, 26, or 56 per- 

 cent, were in process of division, 7 equally and 19 unequally; there 

 were bvids in the oesophageal region of 6, or 13 percent, in the pedal 

 region of 10, or 22 percent; 4 were doubtful cases, due either to bud- 

 ding or unequal fission. About 1 2 percent of the entire number of 

 monogenous polyps, 8 out of 67, were colonies of three or four indi- 

 viduals. These were formed by fission, by budding, or by both 

 combined. 



While budding from the cesophageal region and fission progress 

 very slowly and among a very small number of polyps, basal fragmen- 

 tation produces new individuals very rapidly and is of universal occur- 

 rence. Almost all non-sexually produced polyps therefore arise by the 

 latter process, basal fragmentation. And so, with the possible excep- 

 tion of budding near the foot disk, which in certain respects resembles 

 basal fragmentation, we may disregard both fission and budding, 

 since they play an insignificant part in producing variations in Afe- 

 tridium. 



In a paper on Monogenesis in Metridium published in the Proceed- 

 ings of the California Academy of Sciences in 1S98 I have given 

 (fig. 7, upper left-hand individual in this gi^oup of three) the draw- 

 ing of a diglyphic, hexamerous and approximately regular polyp. 

 Yet this polyp is a product of the non-sexual reproductive process 

 of fission. This is an isolated case, but I hope soon to show that it 

 is not an exceptional one. 



