INHERITANCE IN ASEXUAL REPRODUCTION 



189 



TABLE 15 

 A comparison of the mean number of tentacles of clones T, L, and R 



Difference {T - L) 0.328±0.046 



lost before many individuals had been obtained. However, the 

 difference between this and another clone, L, kept under the 

 same conditions was so marked that it seems certain that the 

 small race represented a distinct genotype. The size relations 

 of the polyps of the two clones is shown in figure 8, taken from 

 camera lucida sketches of estimated average individuals. 



More frequently the differences are less pronounced. Table 

 15 gives the constants obtained for three clones bred during July 

 and August, 1913. Clones T and L were continued after R was 

 discarded and the constants for their full numbers are given 

 separately. They were grown in individual cultures under 

 parallel conditions as in the first experiment and seem to be 

 hereditarily distinct. 



These are the only races which I have cultivated under exactly 

 parallel conditions and no evidence upon the number and variety 

 of such races is available. 



Varieties of Hydra in the earlier literature. The extensive 

 literature dealing with Hydra gives frequent suggestions of the 

 existence of local varieties of the three generally recognized 

 species, and one or two descriptions seems really to establish 

 their existence. The statements concerning the size of H. 

 viridis made by Baker, Trembley, Rosel, Pallas, and Kastner 

 differ considerably but are not conclusive. Marshall ('82) de- 

 scribed a variety of H. viridis from brackish water which remained 

 distinct from the fresh water forms even after cultivation for 



