346 Dr. Franz Low on a new 
What functions this organ peHomns,, and what are its rela- 
tions to the genital organs, is still unknown. Dr. J. Kiihn 
first discovered this or ean in the male of his Anguillula dip- 
sac?, and he also found it impossible to find any data for its 
elucidation in his repeated observations of that worm. With 
regard to the interpretation of this organ (which occurs in the 
males of all the species of the genera Tylenchus, Bast., and 
Rhabditis, Duj.) Lagree rather with Kiihn than with Bastian*, 
being, like the former, of opinion that it is stretched like a 
velum over the anal aperture; whilst Bastian thinks that two 
delicately membranous wings (“caudal ale ’’) are attached to 
the sides of the tail of the male, the contour of which is seen 
under the microscope both in the lateral and dorsal position. 
For if Bastian’s opinion were correct, the membrane must 
appear much narrower in the lateral than im the dorsal posi- 
tion of the animal ; but just the contrary is the case. 
The female genital aperture is also situated near the hinder 
extremity of the body, and leads to a vagina directed vertically 
to the longitudinal axis of the body, which opens outwards 
with prominent margins, and there appears as a short trans- 
verse cleft (vulva). ‘The distance of the vulva from the hind- 
most point is one eighth of the total length of the body. This 
[caudal] part of the ‘body i in the female is always slightly bent 
towards the ventral side, and does not diminish so rapidly as 
in the male. As already mentioned, the granular and vesi- 
cular contents of the body render all inspection of it almost 
impossible; and so I did not succeed in recognizing the in- 
ternal sexual organs, the termination of the intestine, and the 
anal aperture in the female ; on the other hand, I twice saw 
distinctly, in the interior of the body of the female, quite close 
to the vulva, a sharply defined egg, which showed precisely 
the same finely granular contents mixed with a few vesicles 
as the numerous eggs lying loose among the worms. 
Males and females do not differ in length in this species. 
The greater number of them are almost exactly 1 millim. in 
length ; only a few do not reach this size, and remain only 
0°9 millim. long. But as exceptions exist almost everywhere, 
I found among the majority of females of nearly equal length 
one of 1°3 millim. length, and of proportionately increased thick- 
ness. As regards thickness, the males of the same length ap- 
pear to be a little thinner than the females. It is, however, very 
difficult to give perfectly accurate, reliable measurements for 
creatures such as these little worms—as on the one hand, when 
alive they are never still, but are constantly bending, stretching 
* “ Monograph on the Anguillulidee,” Trans. Linn. Soe. vol. xxv. (1866), 
p- 125. 
