50 Trans. Acad. Sci. of St. Louis. 
The same kind of notes were made on 13 of the insects 
from the large, fluffy cocoons in an attempt to detect any 
points which might seem characteristic of this group. 
(See Table 28.) 
Here we have 9 insects which mated normally, and all 
but one yield a very small number of infertile eggs. We 
have also 2 females with the mating period prolonged 
to 36 and 38 hours; here also is a very low per cent of 
infertility. Then we have the opposite extreme, 2 which 
were separated after only 6 and 2 hours in mating, and 
even here the fertility is almost perfect. In the earlier 
series of experiments we were afraid to cut the mating 
shorter than 3 hours, but here a 2-hour period in copulo 
seemed quite as sufficient for perfect results as a much 
longer one.‘* On the whole, the insects from the fluffy 
cocoons show a very slightly higher per cent of infertil- 
ity than the normal Cecropias of this lot, but the infiu- 
ence of two extreme individuals is responsible for this. 
This infertility, however, even if it were more than mere 
chance of this material, could not be of any effect toward 
the elimination of this variety (if these do constitute a 
variety, with their own peculiar characteristics main- 
tained by heredity), because, as we have seen in a pre- 
vious chapter, they produce a larger number of ova than 
do the normal Cecropias. Hence fluffiness is not corre- 
lated with fertility, though it might be with fecundity. 
In this lot we find a low proportion, 5%, of the fertile 
ova which failed to produce larvae. This indicates that 
this group of parents are a vigorous stock. We also see 
in this lot no correlation between early 
sition and infertility. 
For some undiscovered reason, the material of this 
year shows a much lower per cent of infertility than did 
the 1911 collections. Also in this lot we found no indi- 
viduals which, after either a normal, prolonged or short- 
ened mating, still had all of the eggs infertile as we did 
and late ovipo- 
15 See p. 61 for discussion of 1-hour matings. 
