35 
margin of the body is usually Va — V20 the length of the body. 
Stylochiis hyaliniis Bock shows a distance value of V24, and the 
most extreme case is Stylochus nebulosus (Girard), where, according 
to Meixner’s measurements, it is ^/s3. 
In Parastijlochus astis Bock the female orifice has been moved 
so far back that the figure ^/eo is obtained. This distance reaches 
its mininum within the family in Meixneria furva Bock with the 
figure Vi 30 . 
While the genital pores in these two genera never come very 
close to each other (the distance between them is V 9 the length 
of the body in Meixneria and V27 in Par asty lochus), this approach 
is always marked in the numerous Stylochus-species, where we 
may get figures less than Vioo of the body length. 
The enumerated genera agree in the absence of Lang’s glan- 
dular vesicle, a condition that facilitates the decided backward move 
of the female genital opening. 
Group II. There are further four genera with-altogether eight 
species that belong to Stylochidae. These genera agree in their 
possession of Lang’s glandular vesicle. In all of them the male 
aperture lies close to the female one. The accessible figures for 
the distance of the female pore from the posterior body-margin in 
relation to the length of the body give the following results: Neo- 
stylochus fiilvopunctatus Yeri & Kaburaki V 4 , Idioplana australiensis 
Woodworth V 4 , Idioplanoides insignis (Laidlaw) and atlanticus (Bock) 
about Vt, and Limnostylochus annandalei Kaburaki V20. 
Thus, the presence of Lang’s glandular vesicle results in higher 
values, with the exception of the genus Limnostylochus, which we 
shall soon discuss. I might, however, point out here that Limno¬ 
stylochus, as far as the location of Lang’s glandular vesicle and 
the termination point of the uteri, i. e. in respect to the location 
of the proximal part of the vagina, agrees fully with the other 
genera enumerated in Group IL 
Discostylochus lacks Lang’s glandular vesicle. and one might feel 
that for this reason it should belong to Group 1. But, as I shall 
discuss in detail later in this paper, I must assume that the ductus 
genito-instestinalis characteristic for this genus has been derived 
from the duet of Lang’s glandular vesicle. On the basis of this 
assumption, therefore, Discostylochus must be classified with Group IL 
3 * 
