Regeneration 



169 



or full completion of the formation of the oral polyp 

 acted as an inhibition to the further flow of material to 

 this pole. This idea was supported by an observation 

 made independently by Godlewski and the writer that 

 if a piece of stem be cut out of a Tuhularia, and if the 

 piece be ligatured somewhere between the 

 two ends, the oral and the aboral polyps 

 are formed simultaneously. This would 

 be comprehensible on the assumption that 

 the retarding effect which the formation 

 of the oral has on the aboral polyp was 

 indeed of the nature of a flow of material 

 towards the oral pole. 



Miss Bickford' found that the differ- 

 ence in time between the formation of 

 the two polyps disappears also when the 

 piece cut from the stem becomes so small 

 that it is of the order of magnitude of a 

 single polyp. In that case two incomplete polyps are 

 formed simultaneously at each end (Fig. 23). The 

 new head in the regeneration of Tuhularia arises, as 

 Miss Bickford observed, from the tissue near the wound. 

 At some distance from the wound in the old tissue 

 two rows of tentacles arise, which are noticeable as 

 rows of longitudinal lines inside the stem before the 

 head is formed. Driesch noticed that the newly 

 formed head is the smaller the smaller the whole 



» Bickford, E. E., Jour. MorphoL, 1894, ix., 417. 



Fig. 23 



