THE STRUCTURE OF CRYPTOGONIMUS 
525 
tral sucker of the group generally. From its position the anterior 
one would seem more probable, since it is more ventral and nearer 
the surface. But against this view must be noted the position 
of the genital opening which is usually in front of the ventral 
sucker and rarely if ever behind it when in such close relation with 
it . The anatomical situation in regard to these points is decidedly 
novel and aberrant. In the total absence of embryological infor- 
mation and of any closely related forms we shall be forced to leave 
the question of homology unsettled. 
NERVOUS SYSTEM 
The faintly colored minutely granular matterseenin trematodes, 
generally in the chief nervous ganglia, is seen herein sections in 
the position indicated by the letters nv in fig. 2 and in the whole 
worm masses can be seen in this position which are plainly the 
chief nerve mass. In sections nerve cell bodies can be seen on the 
borders of these masses. 
In whole worms a black spot is very distinctly visible on each 
side of the body on the level of the pharynx. Figs. 1-2 show its 
position. They are encountered in the transverse sections where 
they are seen to be very deeply seated. The organ is shown by 
immersion objective to be composed of small rounded grains of 
deep brown color, held together in a mass of oval outline, but no 
special cells can be seen in connection with them. They are con- 
stant in position when present, but in a few individuals they 
are wanting, and in some, one is present and the other is 
wanting. Eyes which are present in early stages of trematodes 
are wanting in the adult stages as a rule (though with numerous 
exceptions, e.g., Cotylaspis, Osborn, '04). In favor of consider- 
ing these pigment masses eyes is the fact of their position; their 
structure does not offer favorable evidence nor their absence in 
some cases. It is, however, possible to regard them as degenerate 
organs of vision, vestigial structures possibly. No traces of other 
sense organs were found. 
