396 READINGS IN EVOLUTION, GENETICS, AND EUGENICS 
true; the yellows when inbred showed themselves to be pure domi- 
nants or “yellows” and dominant-recessives—i.e., splitting up again 
into yellows and whites in the usual proportion. More intricate 
experiments confirmed this general result. 
It must be noted, however, that Coutagne has made much more 
elaborate experiments with different results, which in mamy cases can- 
not be interpreted on the Mendelian theory. Thus he found (1) that 
the hybrid forms were sometimes blends of the parents and different 
from both; (2) that in other cases the brood included some like one 
parent in a particular character, some like the other parent, and some 
intermediate; and (3) that in other cases the individuals showed no 
fusion of characters, but resembled one or other parent. It is likely 
that the discrepancy may be explained as due to considerable diversity 
of origin in the domesticated races of silkworm, so that, while they 
breed true when left to themselves, a disturbance of the usual routine 
leads to the liberation of latent characters. 
Lina lapponica.—Miss McCracken has made a fine study of the 
hereditary relations in this Californian beetle, which occurs in two 
types, spotted (dominant) and black (recessive). They are always 
crossing in natural conditions, but there are no intermediates, and it 
is easy by isolation to rear a “pure” spotted race and a “pure” black 
race. When spotted forms are paired they may produce only spotted 
progeny—a case of extracted dominants. In other cases, however, 
they yield spotted and black forms (1,021 spotted, 345 black), i.e., in 
the Mendelian proportion of 3: 1—a case of dominant-recessives inbred. 
Snails.—Lang paired “pure” five-banded forms of the common 
or garden snail, Helix hortensis, with bandless forms from bandless 
colonies. The young of the first generation were all bandless, the 
banded character being recessive. When these were paired the off- 
spring were bandless and banded in the Mendelian ratio, 3:1. Fur- 
ther experiments confirmed this, not only as regards bands, but also 
as regards colour (yellow or red), size, and the form of the umbilicus. 
It may be said, therefore, that common snails (Helix hortensis and Helix 
nemoralis) illustrate Mendelian inheritance. 
Poultry—Numerous breeding experiments with poultry have 
been made by Bateson, Bateson and Punnett, Hurst, Davenport, and 
others, many of which show Mendelian phenomena with great clear- 
ness, while others are strangely conflicting. One of the reasons for the 
complicated results is evidently to be found in the difficulty of securing 
thoroughly “pure” breeds, for many that breed true as long as they 
