16 DR. F. E. BEDDARD ON 
however, distinctly tubular and definitely opens on to the 
’ exterior, in both of which characters it differs from the cavities 
described above in the young free larva. The water-vascular 
system presents both similarities and dissimilarities in the two. 
In the bud there are but two longitudinal vessels, one on each 
side of the body. These are connected by transverse vessels and 
are thus in all probability to be looked upon as ventral vessels ; 
the dorsal, it is to be presumed, appear later. The youngest free 
larva also possesses only two lateral I$ngitudinal trunks, which 
are for similar reasons to be regarded as ventral vessels; but it 
has in addition other water-vascular tubes which are completely 
wanting in the bud. In fact, there are no detailed resemblances 
such as would be sufficient to overbalance the general unlikeness 
between the buds and the free living asexual parasite; they do 
not appear to me to be stages in the same series. 
§ Origin of the Sexual Form. 
It seems to me to be much easier to believe, on the other hand, 
that the buds area stage in the development of the sexual worm. 
But here it is only a matter of possibility or probability; there 
are but few facts. And these facts are mainly negative. For 
there are actually no more positive points of likeness between the 
bud and the sexual form than there are between the buds and 
the fully developed sexless form; but perhaps the resemblances, 
though few, are of a little more importance. In the first place, 
the solidity of the body anteriorly to the bladder, save for the 
one tube which runs along it, is more suggestive of the adult 
sexual worm, than of the sexless worm with its abundant cavities 
and continuous bladder-cavity. The gradual tapering off of the 
single cell-lined cavity, which the buds possess, as it approaches 
the anterior end of the body, indicates the ease with which it 
may vanish altogether. In the second place, the bud shows no 
series of peripheral tubes which I have regarded, in the case of 
the young free worms, as a part of the water-vascular system. 
These are absent from the sexually mature worm. Finally, there 
are the aggregations of cells, of which I have spoken in my first 
paper upon this worm and which may be the commencing sexual 
organs. 
This is the most important resemblance. The other features 
in the structure of the bud do not forbid the view which I 
am now supporting by such facts as are available. But they 
might with equal reason be urged in favour of a likeness with 
the free sexless stage. 
There is obviously nothing decisive about the retardation in the 
appearance of the smaller dorsal water-vascular tube, and the fact 
that there are two layers of bundles of longitudinal muscular fibres 
in the cortex points with equal directness to the adult worm and to 
the complete immature worm. But the comparison here is with 
the fully developed immature tapeworm, and not with the maggot- 
