Gi) 
occurrence of undoubted cases of fertility in male hybrids has 
been proved by crossing the male hybrids with the females of 
both parent-species, and in one case with the female of a 
third species. 
c. The relative strength of hereditary *nfluences. 
(N.B. The three following conclusions rest on an elaborate 
series of experiments with certain species of Saturnia, and 
are prefaced in the ‘“*‘ Handbuch” by a careful discussion of 
the evidence that exists respecting the relative phylogenetic 
age of the forms in question.) 
5. The freshly-hatched hybrid larva closely resembles 
that of the female parent; but with the process of growth 
a resemblance to that of the male parent gradually 
increases. 
6. The extent of approximation towards the male parent 
depends on the relative phylogenetic age of the two species ; 
the older being able to transmit its properties, whether of 
structure or habit, better than the younger. 
7. In reciprocal pairing, the male is able to transmit the 
characters of the species in a higher degree than the female. 
This influence, however, is less regular and potent than that 
spoken of in the preceding paragraph. 
pv. The result of crossing a parent species with a local race, 
or with an aberration of the same species. 
8. When the normal form of a species (Grundart) is 
crossed with a gradually-formed local race of the same 
species, the result is a series of intermediate forms. 
9. On the other hand, when the normal form is crossed 
with a sporadic aberration, the result in many cases is that 
the issue divides itself sharply between the normal form and 
the sport, intermediate forms being absent. 
To the foregoing summary the speaker added the following 
comments :— 
1. The experiments completely disprove the remarkable 
assertion of Escherich as to the non-occurrence of insect 
hybrids. 
