INHERITANCE IN ASEXUAL REPRODUCTION 159 



perimental zoologists are those of Linnaeus. Brauer ('08) applied the 

 rule of priority, thus requiring the nomenclature of Pallas. In 1912 

 Bedot criticised Brauer 's revision and showed that the species, H. 

 viridis L. should be retained. Since the experimental literature has 

 employed the Linnaean nomenclature this has been used here in order 

 to avoid the constant repetition of synonjans. The names employed 

 are given below at the left, with the revision of Bedot at the right. 



H. viridis L. . H. viridis L. 



H. grisea L. H. vulgaris Pall. 



H. fusca L. H. oligactis Pall. 



H. polypus A. Brauer. 



Experiments of Hanel 



Hanel began her work in 1906 and during the two years of her 

 experiments bred clones from 26 wild Hydras, obtaining records 

 of nearly, 7000 buds, the descendants, by asexual reproduction, 

 of the original 26. Upon comparing these 26 'stem parents' 

 with their immediate progeny she found that those with a large 

 number of tentacles produced buds having, on the average, a 

 greater number of tentacles than the corresponding buds of par- 

 ents with few tentacles. From the progeny of the 'stem parents' 

 taken singly Hanel selected polyps with a high, an intermediate, 

 and a low number of tentacles and continued this selection for 

 from two to seven generations. Averaging the results obtained, 

 she found that within the single clone the mean number of 

 tentacles of the progeny of individuals selected for four genera- 

 tions was slightly less in the group selected for a large number 

 than in the group selected for a small number, whence she con- 

 cluded that variations within the clone are not inherited. 



Criticisms of Hanel' s results 



In 1909 Hase, at the suggestion of Plate, studied the relation 

 of the number of tentacles of Hydra to the age of the polyp and 

 to the number of tentacles of the buds. He verified the obser- 

 vations of Parke ('00) and Hanel that the number of tentacles 

 increases with the age of the polj^ps, finding an average increase 

 of 2.1 tentacles in a number of polyps kept under observation 

 for 90 days. In recording her data Hanel had taken this fact 



