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 in a 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 100 to 150 egg-tubes have no separate 

 investment, instead of which they are surrounded loosely by a 



