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STUDIES ON THE DIGENETIC TREMATODES. 461 
As already mentioned the large ventral sucker surrounded 
by a yellow ring is the most prominent feature seen on 
ventral view. On the dorsal aspect the two intestinal 
diverticula show up very conspicuously by reason of their 
dark green contents. 
The oral sucker is sub-terminal and globular, measuring 
“40-45 mm. The ventral sucker is also globular, situated a 
little behind the centre of the body. Its aperture may be 
either circular, transverse or diamond-shaped. Its diameter 
is °9-1°0 mm., therefore about twice that of the oral sucker. 
Although of such great size, it is deeply sunk into the body 
and does not project much above the surface. 
The histological structure of the suckers, especially the 
ventral sucker, presents many features of interest, and here 
my observations do not entirely agree with those of Jacoby. 
There are three chief varieties of cells: First, the large 
myoblasts (fig. 14, @z). These are extremely few, not 
more than two or three appearing in any one section. They 
are very large cells, measuring ‘05-05 mm., and, as Jacoby 
observed, the cell-body stains homogeneously deep red. The 
nucleus is central and oval in shape, measuring about ‘02 by 
‘015 mm. It is traversed by a well-defined chromatin net- 
work, in the midst of which is situated a globular nucleolus, 
the diameter of which is ‘007 mm. This type of cell differs 
from the myoblasts usually met with in other species, or at 
any rate in the species which I have hitherto examined, 
chiefly in the denser character of the nucleus and its shape. 
These cells, however, have the same situation as the myo- 
blasts im other species, namely, the median zone, midway 
between the outer and inner limiting membranes of the sucker. 
The second variety of cell (tig. 14, pzs ) is that identified 
by Jacoby as the cells which Schwarze! considered as “‘ Reste 
der urspriinglichen Bildungszellen.”’ These are the cells 
marked “«G z” 
if not exclusively, round the aperture of the sucker. They 
in Jacoby’s figures, and they occur chiefly, 
‘Die postembryonale Entwicklung der Trematoden,” in ‘ Zeitsch. f. 
wiss. Zool.,’ xliii (1886), p. 54. 
