Experiments of Cuénot 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 Cuénot 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 
