214 MENDELISM 
of mice. The simplest typical ratio thus produced is 
12¢3 2%. 
4. The last type of latency described by Dr. Schull 
is of a totally different kind. It is represented by the 
phenomenon to which the term ‘ latency ’ was origin- 
ally applied by de Vries. This latency consists in the 
disappearance of certain characters under the influence 
of poor nutrition, or other changes of conditions. 
Examples of this phenomenon described in the chapter 
on Mutation were the submerged and floating leaves 
of the water-ranunculus, and the red and white colour 
of the flowers of a species of primula. 
We may now proceed to pass in rapid review a 
selection of the more remarkable instances of Mendelian 
inheritance which have been so far demonstrated. 
The ease with which characteristics of colour can be 
distinguished and defined has naturally led to a good 
deal of attention being paid to the phenomena of their 
inheritance. In this way many cases of simple domi- 
nance have been discovered in plants and in animals, 
as well as several examples of reversion in F,, followed 
in both cases by a Mendelian segregation of characters. 
Thus the colours of many flowers afford perfectly 
simple phenomena, whilst other cases, like the sweet- 
peas and the closely similar case of stocks studied by 
Miss Saunders, have required long and arduous ex- 
periment for their elucidation. No case of this kind 
hitherto examined has been definitely proved to be 
non-Mendelian. 
Colour characters which follow Mendel’s law have 
been observed in mice, rats, rabbits, guinea-pigs, 
