INTERNAL GENERATIVE ORGANS OF THE FEMALE. 669 
ptera and some Orthoptera, are precisely similar to those of 
the Blow-fly. In those insects, however, in which there are 
but few ovarian tubules, such as Periplaneta, and the Lepido- 
ptera, the structure is somewhat different. In these each egg- 
tube, instead of containing one ripe ovum at a time, contains 
from 20 to 50 or more ina linear series. In these insects the 
egg-tubes are apparently continuous with the oviducts, which 
appear to divide into as many branches as there are egg-tubes. 
Instead of the whole ovary being surrounded by a peritoneal 
capsule, each egg-tube has been described as possessing a 
peritoneal coat; so that, as these investing sheaths of peri- 
toneal tissue are continuous with the peritoneal coat of the 
oviduct, the latter appears to divide into as many branches as 
there are egg-tubes. If, however, the development of these 
ovaries is similar to that of the Blow-fly’s ovary, it appears 
probable that the continuity of the oviducts and egg-tubes is an 
acquired but not a primitive condition. I shall have to refer 
to this hereafter, when I describe the manner in which the 
egg-tubes are developed. 
Histology of the Peritoneal Coat of the Ovary.—In studying 
the writings of various authors on the structure of the ovary 
it becomes evident that the term peritoneal coat is used in a 
very variable sense. Perhaps, strictly speaking, the term is 
not justified at all, but it is convenient and is applied to the 
external connective tissue investment of various organs by 
most writers on the anatomy of insects. The existence of a 
true serous coat is nowhere capable of demonstration. Those 
authors who have denied the existence of a peritoneal coat in 
the case of the ovary have endeavoured to distinguish a true 
serous coat, or have attempted to separate a special coat from 
the capsule of the ovary. The term is usually applied to the 
covering of the individual egg-tubes, when these are few in 
number and easily separated ; and Brandt used it in this sense 
in describing the egg-tubes of Periplaneta. In describing the 
ovary of the field Cricket, Gryllus campestris, the same author 
says, ‘In this insect the r00 to 150 egg-tubes have no separate 
investment, instead of which they are surrounded loosely by a 
