developpes et l’uterus charge d’oeufs en moins grand nombre. < 
observation demontre done que les petits individus sont des jeunes, 
non encore parvenus a toute leur croissance; elle explique en menu- 
temps leur aspect plus clair.” I may confess that for a certain time 
I held a similar view; but it cannot be upheld any longer lor the 
following reason: Supposing that the small individuals were indeed 
young, i.e. in the beginning of the period of their sexual activity, 
one ought to expect that the large individuals would be without 
exception perfectly sexually mature and full of ova. But this is 
actually not the case. In the Hamburg material I have for examina 
tion there are two immature specimens, both with a uterus developed 
to its full length but containing, in the first specimen, only spcrmat< -/■ * 
(the seminal receptacle containing nothing but a number of egg 1 ' 
and in the second specimen a number of loosely grouped ova wh 
are still far from filling the coils as they do in ripe individual 
Nevertheless, these worms are unmistakeable representatives of the 
large species, for they measure, the first 13‘5 by 2-5 mm., the second 
12*5 by 275 mm. ; they show, in addition, the size of the suckers and 
the brown pigmentation distinctive of that form. One similar 
specimen was found in the material from the Port Said case. I- or all 
of them, the explanation alluded to above does not hold good . they 
prove, on the contrary, that the large species when the period of in 
sexual maturity begins has already reached, or even exceeded, tin- 
maximum size of the small form. Unfortunately, the scant material 
I possess of the latter does not contain any young individuals; hut 
the fact just recorded suffices I think to show that the two forms 
cannot be one and the same species. 
If they are different the question arises, whether they are to be 
considered as full species or as mere varieties. I suppose that many 
of my fellow-helminthologists, regarding, in the first place, the aim m 
peifect similarity of the internal organisation, as compared to which 
the differences in size, &c., appear insignificant, would find tin latter 
alternative quite sufficient to cover the facts, assuming perhaps 
so-called “ local varieties.” I unhesitatingly proclaim the former 
as being more logical and more consistent. The chief character of t In- 
species, in contradistinction from the variety, lies in the constancy with 
which it preserves its specific peculiarities. The variety is inconstant n 
a larger or lesser degree and alternates with typical specimens of the 
J 
