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Transactions of the Boyal Society of South Africa. 
somites, the intimacy of the connections of the annuU enabhng the hmits 
of the somites to be easily made out. Each somite consists of an anterior 
annulus which is twice the size of the posterior small annulus, and so 
reminding one of the biannulate somite of Microbdella. Particularly in the 
posterior region of the neck there is distinct indication of the division of 
the large anterior annulus, and so foreshadowing the triannulate somite. 
The anterior extremity, or head, is devoid of transverse annulation, and in 
all probability represents a number of fused anterior annuli as in the case 
of the Ichthyobdellidae in general. At the same time it is to be noted 
that no " capula " is differentiated as in other Ichthyobdellidae; which is 
surprising since the genus resembles Branchellion so closely in the dif- 
ferentiation of the neck and trunk regions that this species, the first known 
of the genus, was included in the genus Branchellion. The anterior 
extremity is furrowed distinctly by longitudinal grooves, which may be 
regarded as an expression of subdued annulation. If such is the case, then 
we have here the initial stages in the differentiation of the anterior 
extremity of the leech body to form the Ichthyobdellid capula. 
In Ozobranchus, then, w^e have a neck region consisting of eight (8) 
somites, and in front of this an area representing, in all probability, the 
"capula" of other Ichthyobdellida. In this connection it is interesting 
to note that this genus shows a primitive condition also in regard to the 
somite which is distinctly biannulate in the neck region, tending to 
become triannulate in the posterior part of the same region, and becoming 
distinctly so in the trunk region, particularly in adults. 
From these facts it is reasonable to suggest that the neck and capula 
of the Ichthyobdellida correspond to eight plus several (8 + several) 
somites. Since the genital apertures are situated at the base of the neck, 
they would fall most probably in somites x and xi, or in somites xi and xii 
respectively. However, since the Glossiphoniidae and Ichthyobdellidae 
are classed as Ehynchobdellidae versus the Arhynchobdellidae (Gnathob- 
dellidae and Herpobdellidae) it is logical to conclude that the position of 
the pores would correspond to that in Glossiphoniidae ; especially so as the 
pores correspond in position in the Gnathobdellidae and Herpobdellidae ; 
and for reasons later suggested in this paper. 
The genital apertures are usually placed by other workers in somites 
X, xi, and later reasons are brought forward to show that this position is 
constant throughout the group. 
In the Glossiphoniidae, as represented by Glossiphonia and its allies, 
there is a slight variation in the absolute and relative positions of the male 
and female genital apertures. As I have pointed out previously (Linn. 
Soc, N.S.W.), we are in a position to trace the original disposition of the 
pores. The various species and genera all agree in regard to the female 
aperture which is situated, in all except G. heteroclita, between the second 
