i5c t. h. morgan. 



The Simultaneous Development of Oral and Basal Polyps. 



As previous work has shown, the " rule " for pieces of the stem 

 of Tubularia is for the oral primordium of the polyp to develop 

 first, and then, after several days for the basal polyp to develop 

 unless stolons have already appeared ; yet not infrequently the 

 oral and basal ends develop simultaneously. In a few instances 

 the basal hydranths may appear before the oral. It was first shown 

 by Driesch and afterwards confirmed by myself that the time of 

 appearance of the oral hydranth depends on its distance from the 

 oral end. The same relation is observed for basal polyps also. It 

 is therefore of some interest to compare the time of regeneration 

 of oral and basal polyps in those cases where both polyps appear 

 simultaneously to see if any acceleration or retardation can be 

 observed. 



In one case after 50^ hours 23 of 75 pieces showed the 

 beginning of oral primordia. There were amongst these, three 

 "double" pieces, i. e., pieces with both oral and basal primordia. 

 In two of these the oral end was more developed ; in one the 

 basal end was ahead. After another 24 hours there were 43 

 oral primordia, of which 21 were on "double" pieces. There 

 were also 3 pieces with only basal primordia. Thus at first there 

 was an excess of oral development, but the number of basal pri- 

 mordia increased at the second observation. A large number 

 of pieces had not produced as yet the oral primordia, and three 

 of these pieces had basal primordia only. The results show that 

 both ends may develop simultaneously, and in such cases the 

 rate of development may not be behind that when only one end 

 develops. It is evident therefore that, if the stimulus to develop 

 is present, two polyps may develop at the same rate as does a 

 single one. 



In another case, after 45 hours, 56 of 92 pieces had oral pri- 

 mordia only. Twenty-four hours later there were 28 double 

 pieces. In another case after 45 hours, 27 of 55 pieces had oral 

 primordia only. Twenty-four hours later there were 27 oral pri- 

 mordia, and in addition 18 double pieces. 



In another case, after 48 hours, 10 of 29 pieces were double ; 

 of these 6 were equally developed at each end, 3 had the oral 

 end ahead and 1 the basal. In another case at another time, after 



