AVIAN CESTODES. 873 
paruterine organ, thus incidentally proving that the organ is a 
paruterine organ, if any doubt could be supposed to attach to 
that identification of it. The embryos were not directly imbedded 
in the lax tissue of the paruterine organ but were accompanied 
by a cavity within which they lay. Whether this means that 
their assumption into the paruterine organ resulted in the for- 
mation of a cavity by stretching or other means, or whether a 
portion of the uterus was detached as a whole and engulfed by 
the paruterine organ, I do not know. 
$ The Uterus. 
Although the appearance of the paruterine organ before the 
uterus is developed proves that the former is not a product of the 
latter, it does not follow that there is no connection at all between 
these two organs in their origin. I believe that I have been able 
to establish a connection between the two, and that the tissue of 
the paruterine organ gives rise to the uterus. I am not sure 
that 1 have detected the uterus in the very first segment in 
which it is developed, but if not, | am not more than three or 
possibly four segments out. As is often the case with tapeworms, 
the uterus appears rather suddenly and in an advanced stage of 
development, at least speaking relatively. Im the segment in 
question, which is the second or third with a uterus, the testes 
are still active and the ovary and vitelline glands in full maturity 
and not beginning to degenerate. The paruterine organ is 
considerably younger than that represented in text-fig. 5; in the 
sections (which were nearly accurately horizontal) the outline of 
the paruterine organ was nearly square, the breadth being a little 
greater than the length. The uterus consists of an irregular tube 
running rather obliquely across the long axis of the body. The 
tube branches somewhat and there are indications of anastomoses ; 
but the retiform stage of the uterus has hardly been reached. 
The uterus does not extend, as it does later, in front of the 
transversely running coil of the vas deferens. It does not. 
therefore, come into contact with the broad posterior end of the 
paruterine organ as it does in later stages (cf. text-fig. 5). There 
is, however, a connection between the two which is more than 
mere juxtaposition and is, therefore, of an interesting nature. 
A process extends backwards from that posterior corner of the 
paruterine organ which is furthest away from the pore side of the 
segment. It consists, like the paruterine organ at this stage, of 
little more than an agglomeration of nuclei. This process 
extends backwards until it reaches the uterus with whose walls 
it is continuous. 
In an earlier stage, about three segments in front of that just 
described, a uterus can hardly be said to exist. I detected, 
however, a thread of paruterine tissue extending towards the 
same side of the body ; this came into close relations with one or 
two spaces containing ripe ova situated in front of the uterus, 
