452 Prof. R. Leuckart on the Developmental 
otherwise still perfectly concordant females. At this time the 
genital sac measures about 0°15 millim., or more than half the 
length of the chyle-intestine, which, like all the rest of the body, 
has hitherto increased but little in length. After the change of 
skin, the growth advances far more rapidly, with increasing 
sexual development, especially in the female individuals, which, 
at the time of copulation, are about 0°65 millim. in length, while 
the males scarcely measure more than 0°50 millim. The trans- 
verse diameter also is pretty considerable, still especially in the 
females (at the level of the genital orifice, about the middle of 
the intestine = 0:05, in the males only 0:037 millim.), so that 
the form of our animals cannot well be denominated slender. 
In accordance with this, the movements in general are slow and 
clumsy. 
In the female apparatus we distinguish, besides the two ova- 
ries, which run through almost the whole length beneath the 
intestine, and the short vagina with its thin chitinous tube 
seated perpendicularly upon the outer mteguments, also a mid- 
dle section of moderate length, the walls of which possess a dis- 
tinctly cellular structure. From its position, this section repre- 
sents the so-called uterus of other Nematoda; but this denomi- 
nation is perhaps not very applicable in this case, although in 
pregnant individuals it assists in the reception of the young. 
Before the development of the latter it is very distinctly and 
sharply marked off from the extremely thin-walled ovarian tubes, 
the contents of which are formed, throughout their whole length, 
of coarsely granular ova. In the blind extremities of the tubes, 
which are sometimes extended and sometimes bent in the form 
of horns, the ova are but small. But this is not the case at their 
commencement, where, at the time of copulation, we find ova 
fully 0-04 millim. in length (transverse diameter 0°013, germinal 
vesicle 0-008, germinal spot 0:0016 millim.). The number of 
these large ova is, however, but small, rarely exceeding four (in 
winter scarcely ever more than two). 
The male apparatus, as usual, consists of a single testis, which 
runs backward beneath the intestine in the form of a thin-walled, 
usually simply extended tube, and, before its union with the end 
of the intestine, is produced into a short and muscular vas de- 
ferens. Beside the cloaca there are two short lanceolate spicula, 
which, with a third smaller chitinous piece, function as the co- 
pulatory organ. All three are produced by local development 
from the originally quite simple chitinous tube of the extremity 
of the intestine, as is also observed to be the case in other 
Nematoda. The short caudal point of the male is incurved and 
beset with a few small papille to the right and left of the median 
line. The extreme end bears a larger cylindrical papilla. 
