NEW AVIAN CESTODE. 413 
the expense of the ovary. At first it keeps its well-defined 
crescentic shape, but becomes crammed with ova, and finally 
expands so as to occupy nearly the whole of the segment. Mean- 
while the rest of the genital organs become broken down and 
disappear, though for a long time the outlines of the now vacant 
testes can be seen, and the receptaculum seminis and vas deferens 
are still distinguishable by reason of the spermatozoa contained 
in them. 
General Remarks. 
Tetrabothrius strangulatus is distinguished from other members 
of the genus by some interesting peculiarities, quite apart from 
its size, which is unusually small, 
One of its most distinctive features is the very sharp demarca- 
tion of the head from the neck, giving the worm a “strangled ” 
appearance. In other forms the head, behind the suckers, 
usually passes almost imperceptibly into the neck, and there is 
not, as in this species, any considerable portion of the head 
between the posterior border of the suckers and the beginning 
of the neck. 
The small number of testes is also characteristic. As stated 
previously, they do not exceed 9 in number, and the usual com- 
plement is 8. In the majority of species of this genus there 
are at least 22 testes (according to Fuhrmann). There may be 
almost any number up to 60, and the number in a given species 
generally varies slightly, but only in one species hitherto described 
ure there as few as 8 (7. monticellii Fuhrm., from Fulmarus 
glacialis. ‘Testes 8-12). 
In the general arrangement of its internal organs 7. strangu- 
latus approaches closely to 7’. heteroclitus Diesing. But this is a 
considerably larger form, and its testes, though arranged some- 
what similarly in a rosette or horseshoe pattern, are much more 
numerous, and smaller in proportion. Fuhrmann* gives the 
number as 28, but in some specimens in the British Museum 
I have counted 43 in several successive segments, and some- 
times an even larger number (probably about 50) +. 
In conclusion it may be mentioned that hitherto no species of 
Tetrabothrius—nor, so far as I am aware, any other Cestode—has 
been recorded from Diomedea irrorata. 
* Proc. Roy. Soc. Edinburgh, xxii. 1899, p. 649. 
+ ‘The specimens of J. heteroclitus referred to are the types of “ Tenia dio- 
medee”’ v. inst. and “ Tenia sulciceps”’ Baird, respectively, both of which 
Dr. Fuhrmann considers identical with Tetrabothrius heteroclitus Dies. After 
examining specimens of both, in spite of the discrepancy in the number of testes— 
43 in“ T. diomedee”’; about 50 in “ T. sulciceps””—I have no doubt that this view 
is correct. 
