50 
constricted, while that lying anterior to the sucker is in a decided 
State of contraction, connected as it is with the existence of a very 
thick ventral inner longitudinal muscular layer, which is lacking 
in the post-cotylean part, the disproportion between the prae- and 
post' cotylean section is without doubt much larger in the creeping 
animal, the relation probably being about 1:20. The disc of the 
sucker measures 0,5 in length. The sucker has a stem that is 
short and thick. 
Arrangement of eyes: The two cerebral eye-clusters meet 
anteriorly. Posteriorly they diverge and each cluster consists of 
Text-fig. 15. Euprosthiostomum adhærens. Arrangement of eyes, 48 x. 
The tour eyes marked black are ventral eyes. The sense furrow is also drawn. 
about 10 dorsally located ocelli. Nearer the ventral side of the 
animal there are two more eyes on the lateral side of each of the 
clusters mentioned above. These are shown black on text-fig. 15 
and belong of course to the cerebral clusters. However, they are 
on a level with the brain, and not close to the dorsal muscular 
Wall of the body. The openings of their cups are turned toward 
the ventral side of the body. They represent the ventral eyes 
mentioned by Lang for a number of Cotylean genera. 
The marginal eyes form a half-circular band reaching to the 
region of the pharynx. In the most anterior part of this region, 
there are also a couple of scattered ocelli. Between the cerebral 
and the marginal eyes, on each side of the median line, there are 
also a few ocelli, which in analogy with the condition in the Aco- 
tylean genus Stylochus, I shall call frontal eyes. These, as well as 
