68 
DARWINISM 
CHAP. 
organs of a species of earthworm (Perionyx excavatus). The 
normal characters of this species are— 
Setae forming a complete row round each segment. 
Two pairs of spermathecae—spherical pouches without 
diverticulse—in segments 8 and 9. 
Two pairs of testes in segments 11 and 12. 
Ovaries, a single pair in segment 13. 
Oviducts open by a common pore in the middle of 
segment 14. 
Yasa deferentia open separately in segment 18, each 
furnished at its termination with a large prostate 
gland. 
Between two and three hundred specimens were examined, 
and among them thirteen specimens exhibited the following 
marked variations :— 
(1) The number of the spermathecse varied from two to 
three or four pairs, their position also varying. 
(2) There were occasionally two pairs of ovaries, each 
with its own oviduct; the external apertures of 
these varied in position, being upon segments 13 
and 14, 14 and 15, or 15 and 16. Occasionally 
when there was only the normal single oviduct 
pore present it varied in position, once occurring on 
the 10th, and once on the 11th segment. 
(3) The male generative pores varied in position from 
segments 14 to 20. In one instance there were two 
pairs instead of the normal single pair, and in this 
case each of the four apertures had its own 
prostate gland. 
Mr. Beddard remarks that all, or nearly all, the above 
variations are found normally in other genera and species. 
When we consider the enormous number of earthworms 
and the comparatively very small number of individuals ex¬ 
amined, we may be sure, not only that such variations as these 
occur with considerable frequency, but also that still more 
extraordinary deviations from the normal structure may often 
exist. 
The next example is taken from Mr. Darwin’s unpublished 
MSS. 
