244 Trochosphsera sequcitorialis. By Herr Semper. 
which make up the width of the band (9 o o). As the animal grows 
older this stretches itself lengthwise, the cells arrange themselves 
in a single row, so that the breadth of the ovary, i. e. at the end 
belonging to the oviduct, is always filled up by a single egg (10/). 
Of the small nuclei (9) originally round, constituting the un- 
developed eggs, which afterwards were no longer recognizable by 
their varying contours, the star-shaped ones (10 /) grew large ; 
the eggs themselves, although without any covering, separated 
themselves sharply from one another, especially towards the oviduct. 
This is uncommonly delicate, but capable of stretching to an extra- 
ordinary extent ; it is formed directly by the lengthening of the 
exceedingly thin tunica propria of the ovary, and appears not to 
possess an epithelium. It joins the cloaca (9) so as to be just in 
the middle (1) between the points of junction of the excretory 
ducts. 
As soon as the egg passes into the oviduct, the nucleus con- 
tracts to a round bladder (10 b) ; but even here no egg-skin forms 
itself. Then it reaches the cloaca (10 a) without an egg-shell being 
formed even here, and here it develops into a young animal, which 
corresponds exactly to the mother in all particulars, even in the size 
and manifest separation of several inner organs (11). At the 
beginning of my investigations, October 14-16, 1859, I found a 
number of specimens with developed eggs in the ovary and oviduct, 
but only occasionally one with an egg in the cloaca. From October 
18-20 all the larger specimens had eggs already developed, with 
generally one in the cloaca, sometimes two, in one case even three ; 
then they were always in different degrees of development. Lastly, 
from October 25 to the beginning of November almost nothing but 
young. Development then seems to progress exceedingly rapidly, 
as was to be expected from the high and uniform temperature 
of the streams in the Philippine Islands. 
My reason for calling these female was because the principle 
of the contrast formerly supposed between the real egg and the 
germ (ovum and pseud ovum) cannot be maintained unswervingly 
according to the latest investigations on parthenogenesis. I cer- 
tainly believe that I only discovered female Trochosphaera, which 
multiplied by parthenogenesis ; for in all the hundreds of speci- 
mens which I observed, I never succeeded in discovering undoubted 
males nor zoosperms in the cloaca of specimens containing eggs. 
A short time after making these observations I was obliged to 
leave Zamboanga ; and on returning three months later, and look- 
ing for my Trochosphaera in the same ditches, I could not find a 
single specimen. If we might suppose that in this interval sexual 
generation had begun, the succession of the two modes of genera- 
tion there would correspond to ours here, i. e. in the heat of summer 
parthenogenetic generation, on the approach of the cold season 
