Experiments of Cu&iot and Castle 



respective grandparents, and these should breed 

 absolutely true, if the segregation of the 

 gametes is as pure as the Mendel's law seems 

 to require. 



There are, however, certain facts, which recent 

 experimenters have brought to light, that seem 

 to show that the segregation is not so com- 

 plete as the law requires. For example, 

 the so-called pure extracted forms may be 

 found, when bred with other varieties, to have 

 some latent characters. Thus Cuenot observed 

 that extracted pure albino mice, that is to say, 

 those derived from hybrid forms, did not all 

 behave alike when paired with other mice. 

 Those which had been bred from grey x white 

 hybrids behaved, on being crossed, differently to 

 those that had been bred from black x white 

 hybrids ; and further, those derived from yellow 

 x white hybrids yielded yet other results on 

 being intercrossed. Castle records similar pheno- 

 mena in the case of guinea-pigs, and accordingly 

 draws a distinction between recessive and latent 

 characters. Recessive characters are those which 

 disappear when they come into contact with a 

 dominant character, but reappear whenever they 

 are separated from the opposing dominant char- 

 acter. Latency is defined by Castle as "a con- 

 dition of activity in which a normally dominant 

 character may exist in a recessive individual or 

 gamete." 



149 



