232 Henry LestıE OsBoRx, 
and pushing it out and drawing it back. The mouth funnel at this 
age is, as in the adult, not a true oral sucker, 2. e. there is no 
distinct muscular organ with an internal limiting membrane. The 
ventral sucker is relatively much smaller than in the adult (Fig. 73, 
74 and 75) and entirely simple, the sub-divisions so characteristic 
at a later stage have not commenced to form, the worm is about 
in the same stage as that of VoELTzkow’s fig. 43. The inner 
anatomy of this young individual is indicated in Fig. 75. There is 
a prepharynx, pharynx, no oesophagus and an intestine. The 
anterior end is at times thrust very far forward and again drawn 
back so that the prepharynx projects into the mouth funnel (Fig. 76, 
77). Eyes are wholly wanting. This seems rather strange, for they 
are a conspicuous feature of the younger adult and degenerate in 
the older ones so that we should expect them to be present at this 
stage, they evidently arrive late and depart early in the ontogeny 
of Cotylaspis, wnlike Distomes in which they are present only in 
the Miracidium stage and are regarded as reversionary. The ex- 
cretory system is developed as to the vessels, bladders and pores, 
but there are two distinct and widely separated bladders and pores, 
an entirely independent system for each animal. The cuticle has 
already reached its adult condition, no cells or traces of nuclei are 
to be seen in it, but it is thinner than in the adult. Wrinkles of 
the cuticle as in the adult were seen in the young one during 
retractions of the head. The parenchymatous glands (Fig. 79) were 
seen ending in the cuticle, their terminations seen by careful 
focussing as in Fig. 78. In profile views the glands extend slightly 
beyond the general level of the cuticle. The sense organs of the 
cuticle could not be seen and seem not to have developed as yet. 
Although the movements of the animal appeared to be perfectly 
performed, the muscular layers of the body wall were not fully 
formed, the circular fibres being scanty and the oblique layer 
wanting entirely. The ventral sucker is covered with its cuticle, 
and the muscular tissue is in the form of one large mass, limited 
by a distinct membrane on the inner side, but showing no signs of 
the sub-divisions later to appear. The sucker has the appearance 
of that of a Distomid, there being no indications of the sub-divisions 
later to appear in it. The sucker at this time is very large and 
conspicuous, bulging out very much beyond the contour of the 
animal. The parenchyma is mature, made up of branching nucleated 
cells, but no traces of the diaphragm have as yet appeared. The 
