Experiments with Snails, Moths, and Beetles 141 
Individuals of these two species also show other antagonistic 
characters. There are size differences, and these also Mendelize. 
The form of the navel also differs and gives a fourth character. 
The preceding breeding experiments relate to differences 
within the species, but Lang has also carried out experiments 
between the two species, H. hortensis and H. nemoralis. The 
results will be described in the next chapter. One point of 
interest must, however, be mentioned here. As stated above, each 
species contains individuals that are banded or bandless, red 
or yellow, etc. These are varietal differences. The point of 
interest is that when the two species are crossed the offspring — 
species hybrids — show that one of the antagonistic characters 
dominates in the same way as when the varieties within the spe- 
cies are crossed. For example, if a bandless individual of Helix 
hortensis is paired with a five-banded individual of Helix nemo- 
ralis, the hybrids are in some cases entirely bandless, in other 
cases partly bandless and partly five-banded. ‘Lang accounts for 
these results by assuming in the first case that a “ pure’ bandless 
form was used, all of whose germ-cells were “‘ pure’ and hence 
dominated; while in the other case a dominant recessive was used 
which would produce both kinds of germ-cells. Ontheotherhand, 
one should not lose sight of the fact that the hybrid-crossing may 
itself set ‘“‘free”’ latent characters, as in mice, so that the results 
may have arisen in this way.. Lang concludes that those varietal 
characters that Mendelize within the species behave in the same 
way when different species are crossed. 
Experiments with Silkworms 
Elaborate series of experiments with silkworms have been 
carried out by Coutagne.’ The results of ten years’ work were . 
published in 1903. Although ample evidence is furnished of 
alternative inheritance, the results are not treated by the author 
from the point of view of Mendel’s law, although there are indica- 
tions in many places that some at least of the results might profit- 
1 Bulletin Scientifique de la France et de la Belgique, XXXVII, 1903. 
