THE SCOLEX POLYMORPHUS 825 
thobothrium, but without hooks.’’ And finally, others which 
had ‘‘red pigment, two costae, one specimen noted with rudi- 
mentary hooks (Calliobothrium or Acanthobothrium)” and in 
another lot a specimen is recorded with the ‘“‘rudimentary hooks 
and pigment spots.” 
Under the parasites of the sole, Symphurus plagusia, there are 
mentioned specimens which are ‘‘comparatively large, with two 
costae and red pigment like young Acanthobothrium, but without 
hooks.” 
Fig. 80, plate 12, shows a young specimen of Calliobothrium 
with rudimentary hooks, but otherwise much like the Scolex 
polymorphus. 
In view of these later observations of Linton and Monticelli’s 
results, one would expect the Scolex polymorphus from about 
Woods Hole to develop into one of the species of Calliobothrium 
found in this region, or perhaps some other species of the family 
Onchobothriidae, and this last is what I believe happens in the 
case of the larvae with which my experiments were performed. 
Since two species of the genus Calliobothrium (C. verticilatum 
and C. eschrichtii) have been found in our region, by Linton (99) 
who records this species from the dogfish (Mustelus canis), and 
since a considerable number of species belonging to most of the 
genera of the family Onchobothriidae have been described from 
Woods Hole by Linton, it would seem not at all unlikely that 
experiments made by feeding the Scolex polymorphus from the 
various teleosts to skates, dogfish and sharks might connect 
these larvae with other genera of the Onchobothriidae. Such 
experiments would be likely to give precise evidence for or against 
Linton’s belief that the larvae represent the young of more than 
one form and they might give us data for further consideration 
of the whole question of xenositism, which Linton suggests is 
the condition of these larvae when found in teleosts. 
In considering the possibility that the various forms of erus- 
tacea are the true intermediate hosts in which the development 
was begun, I have made a careful tabulation of the food of these 
fishes as recorded mainly by Linton (’99), but also in more detail 
for a smaller number of fishes in tne work of Peck (’95). This 
