DEVELOPMENT OP TIIE OVARIES IN THE BLOWFLY. 431 
Stein describes it as opening on the ventral surface in Beetles. 
I formerly fell into tlie same error ; and it is exceedingly difficult 
in dissections to determine this point. Sections of the entire 
insect show at once the true relations of the parts. 
The pouch-like anterior part of the vagina is very distinct from 
the posterior part ; that portion of it in front of the orifice of 
the common oviduct (fig. 3, b ) in the young insect is the bursa 
copulatrix of authors. The bursa in the egg-laying insect is no 
longer distinct, but forms the anterior part of the vaginal pouch. 
I shall call the vaginal pouch the uterus, a term applied to it 
by Palmen (21) to distinguish it from the posterior tubular part 
of the vagina. If the term is not morphologically, it is at least 
physiologically correct, as an egg is frequently retained in it 
until the embryo is ready to escape from the shell. 
There is at present some uncertainty as to the exact manner in 
which the common oviduct is developed ; although it is quite 
certain that the ovarian ducts are developed from the posterior 
portion of the ovary, as Palmen has distinctly shown (21). The 
same observer also shows that the vagina, uterus, and their appen- 
dages are formed by an invagination of the external integument, 
or rather of the hypoderm. My own observations entirely con- 
firm Palmen’ s statements. Although I have not been able to 
trace the development of the common oviduct, its structure and 
the manner in which the common duct of the testicles is formed 
in the Ply (Weismann, l. c. Taf. xiv, fig. 68) indicate that it is 
formed from the prolonged posterior parts of the ovaries. 
So far I have stated nothing concerning the anatomy of 
these parts which has not been frequently observed and generally 
admitted. I must now, however, enter into some details which 
are not, so far as I know, to be found elsewhere. 
The common oviduct in the Blowfly terminates in tw T o distinct 
enlargements (figs. 1 and 3). The more anterior is due to a 
thickening of its muscular coat where a thick retractor muscle 
(m) is inserted into it. This witndraws the parts with the ovi- 
positor. The second or terminal enlargement (os) is, however, a 
pouch or bulb lined by a greatly plicated intima, and capable of 
distention, so that it encloses the entire egg during its passage 
through the oviduct. One egg is frequently found in this section 
of the oviduct Avhilst another occupies the uterine cavity. 
