212 
Is Pedalion a Rotifer ? 
in which I have drawn them ; but so fill the posterior extremity 
that there would be no apparent difficulty in the aperture’s being 
at (g). After I had seen the faeces expelled and had ascertained 
the true position of the anus, I was still puzzled with the spot ( g ). 
There was an appearance of corrugated skin overlying the ventral 
surface round about it, which made me fancy at first that the 
particular animal I was looking at was unhealthy, or had suffered 
some accident ; and that the projection at {g) was not normal. 
However, this explanation would not do, for almost every specimen 
had the same appearance. It is only quite lately that I arrived 
(as I believe) at the right conclusion. I had the good fortune to 
find a Pedalion with an almost empty stomach and intestine, with 
a skin brilliantly transparent and quite free from the various 
parasites that often mar its beauty. The first glance at this gem 
showed me a muscle which had before escaped me, and which I 
have described above, and drawn in Fig. 2, c. The second showed 
me another new pair of muscles (Fig. 2, d), each with one 
branch attached to the posterior extremity and the other at ( g ), 
the broad attachment being at (e), and the effect of the whole 
arrangement to give a sideways pull at {g). It occurred to me at 
once that this must be the aperture of the oviduct, and that the 
corrugated skin surrounding it is due to the distension caused by 
the passage of the large eggs. It is true that such an aperture is 
almost an unheard-of luxury in a rotifer, and that Asplanchna, I 
think, alone possesses one ; and in its case the aperture is a necessity, 
not a luxury ; for without it this unhappy rotifer would have to 
expel its young as well as its faeces from its mouth. But the 
ovarian apparatus in Asflanchna is precisely similar, and I have seen 
it used ; I have seen the aperture opened by its proper muscle, and 
the young Asflanchna expelled. The obvious way to determine the 
point would be to watch Pedalion laying an egg ; but although I 
have had scores of specimens under observation I have never seen 
an egg laid. I watched in vain one specimen, in which there was 
an egg apparently nearly mature, for upwards of two hours ; and 
then I desisted, for eyesight is more precious than rotifers. It is, 
however, of little consequence, for rotifers are so constantly laying 
eggs that some observer is sure to see the process next year. 
Pedalion lays both female and male eggs, and, with respect to 
them, resembles the majority of the rotifers in the following points ; 
viz. eggs of different sexes are not found on the same individual ; 
virgin females lay female eggs during the greater part of the year ; 
male eggs are half the size of female ones, and are carried in 
clusters of often a score at a time ; and, finally, the males are small 
abortions without any organs for procuring or digesting food, 
appear at only one period of the year, and live a very short time — 
