The Rot in Sheep. 
109 
mixinji; tlie whole up together in one illustration. The generative 
appendage is strongly muscular, especially on the side of its 
curvature, as is attempted to be depicted by the lines there 
drawn. In addition to its longitudinal order of fibres, it has 
also a circular set, which are well developed. When fully pressed 
out the appendage curves upon itself, and always in proportion 
to the amount of pressure which is employed to produce its 
exsertion. It is also found to have a cauliflower-like projection 
at its extreme end, which otherwise is of a rounded form. It is 
imperforate at its extremity, for the duct which enters its base 
from the receptacle within its sheath only extends about a 
third part of the entire length of the appendage, where it abruptly 
terminates. 
It has been supposed, but erroneously, that a canal runs 
through the whole course of the organ, and in several illustra- 
tions of it such a passage is represented. We quote Professor 
Owen's remark on this point, which must suffice to show the 
general opinion of naturalists : " This appendage," says this dis- 
tinguished professor, "is spirally disposed when flaccid, is tubular 
and distinctly perforated at the apex." * 
The extraordinary curving of the appendage upon itself when 
completely exserted, and therefore under circumstances analogous 
to its erection, seems to us to militate greatly against the opinion 
of its being used as an intromittent organ, in the true sense of 
the term ; whilst its size likewise negatives the idea that it can 
be made to enter the mouth of the oviduct as it would have to do 
in ordinary copulation. If contact for fructifying the ova does 
take place between two distomata, but which we very much 
doubt, it would appear that the generative appendage of one 
could only enter the sulcus which is produced by the retraction 
of the organ into its sheath in the other of the two creatures thus 
engaged. In being fully retracted, however, the appendage 
appears to simply lie within the sheath ; and it is very probable 
that its retraction is chiefly needed for the purpose of giving a 
facility to the escape of the ova from the oviduct, as previously 
explained. 
Nervous system. — In concluding our description of the anatomy 
of the distoma we add one word respecting its nervous system. 
Mehlis, some years since, described the nervous system of the 
entozoon as consisting of " a delicate oesophageal filamentary 
ring, with a slight ganglionic enlargement on each side, from 
which minute fibres pass into the suctorial sphincter ; and two 
large filaments pass backwards, one on each side, as far as the 
ventral sucker " (^Oiven). We are free to confess that up to this 
time our investigations have not satisfied us of the existence of a 
* ' Lectures on Invertebrate Animals.' 
