. H. G. Jackson 
53 
Similarly the Nairobi specimens can be referred to the variety originally 
described by Railliet under the name of F. hepatica var. angusta, from which 
they only differ in the slightest degree. The Rhodesian flukes possess no 
character which would separate them from either, the first collection coming 
nearer to the Rangoon specimens and the second collection to the Nairobi 
specimens. 
The bridge between the two forms being thus complete, it may be taken 
that F. angusta and F. aegyptiaca are one and the same species. 
Their relation to F. gigantica is less obvious. The great size of Cobbold’s 
specimens may partly be accounted for by the undoubted maceration they 
had undergone before examination. Goddard (1919) records cases of extreme 
alterations in Fasciolopsis , measured immediately after evacuation and after 
standing a few hours in water. Shape and size cannot count for a great deal 
in the delimitation of species in these forms, owing to the distortion inevitably 
produced by maceration and fixation, unless coupled with distinct anatomical 
differences. 
The anatomy provides us with little on which to base a separation. The 
alimentary canal is provided with the ramose internal branches of the diver¬ 
ticula, which have been shown to be characteristic of all the forms described 
above. 
Cobbold’s figures do not distinctly show the proportion of pharynx to 
oesophagus, but it is indistinctly indicated (it was not possible to make out 
the point in the original specimen I examined) that the oesophagus is quite 
as long as the pharynx. If this is correct—and the mobility of the muscular 
pharynx makes the character at least of doubtful value—it makes a point of 
difference from these recent specimens. The testes are similar and occupy 
a similar proportion of body space. The remaining organs are similar. The 
parasite comes from the same continent as all the elongated forms (except 
the Rangoon specimens) that have been hitherto described. 
The eggs—length 0-145 mm. to 0-150 mm., breadth 0-082 mm. to 0-088 mm. 
lie within th^ limits of those of the specimens described above. 
On the whole therefore the differences amount to so little that we may, 
without much hesitation, refer all these forms to the species Fasciola gigantica 
(Cobbold). 
The descriptions given above may now be combined to make the following 
diagnosis of F. gigantica. 
F. GIGANTICA (COBB.). 
Body elongated and at least three times as long as broad. Cone passing 
almost insensibly into the body, prominent “shoulders'’ always being absent. 
As a rule the sides of the body are roughly parallel and the posterior extremity 
is bluntly rounded or more rarely bluntly pointed. The ventral sucker is large, 
often protuberant and its cavity is usually prolonged backwards into a blind 
pouch. The pharynx is longer than the oesophagus. The external branches of 
