Various Opinions on Heredity. 115 



be more correct to say that the elements of both parent 

 species exist in every hybrid in a double state, namely, 

 blended together and completely separated." 



In another place (Variation, ii. p. 80) he says: "On 

 the doctrine of reversion, as given in this chapter, the 

 germ becomes a far more marvellous object, for besides 

 the visible changes to which it is subjected, we must be- 

 lieve that it is crowded with invisible characteristics, 

 proper to 'both sexes, to both the right and left sides of 

 the body, and to a long line of ancestors, male and fe- 

 male, separated by hundreds or even thousands of gen- 

 erations from the present time, and these characters, 

 like those written on paper with invisible ink, all lie 

 ready to be evolved under certain known or unknown 

 conditions." 



I shall discuss the phenomena of reversion somewhat 

 at length in another place, and wish to simply call atten- 

 tion at present to the fact that here, as in the case of 

 secondary sexual characters, we have a much simpler ex- 

 planation in the hypothesis of arrest, and therefore do 

 not need to call in an unknown factor, such as the mul- 

 tiple personality of each individual. 



I think that the phenomena of alternation of genera- 

 tions favor this latter supposition even more than the 

 facts of reversion. 



The egg-embryo of a hydro-medusa may give rise by 

 budding to an indefinite number of hydroids like itself, 

 and each of these may give rise to other hydroids, and so 

 on indefinitely. 



Each one of these may also, under certain conditions, 

 give rise to medusas quite different from the hydroids 

 and like the original medusae. As the medusae which 

 are thus produced inherit through a long series of hy- 

 dra ancestors ull the specific characteristics of the origi- 



