228 



AYEES ON THE DEVELOPMENT 



OECANTIIUS NIVEUS. 



The sexually mature ovaries of Oecanthus are - bodies about the size and shape of an 

 apple seed. They lie in the abdominal cavity above" the alimentary canal, and on account 

 of the mass of eggs contained in them completely fill, or even distend this cavity beyond 

 its normal capacity. They are united anteriorly into a common terminal cord which is 

 inserted in the wall of the dorsal vessel, in the thorax above the stomach. The origin 

 and growth of this cord and of the ovaries is best seen in the embryo. From this point 

 of insertion they are directed backwards, downwards and outwards, and terminate in the 

 oviducts. They are held in place by connective tissue filaments, the peritoneal lining and 

 the ramifying tracheal and nerve filaments. 



The oviducts extend inward from their origin on the ovary and unite into a common 

 duct, the vagina. At this point of union is given off the receptaculum seminis as a pouch 



from the wall of the vagina. At its posterior 

 outlet the vagina is connected with the genital 

 armature. Each ovary consists of from 10 to 

 20 * delicate, thin-walled egg tubes or ovarioles 

 covered by a net-like peritoneal membrane. 

 This net is composed of cell-groups connected 

 by narrower portions of the cellular membrane. 

 These groups are composed of relatively large 

 cells with finely granular, scarcely stainable 

 protoplasm and a central deeply stainable 

 nucleus. The ovarian tracheae ramify through- 

 out this coating but do not connect with the 

 tunica propria of the ovariole. This covering 

 for the sexual organs is continuous with the 

 peritoneum of the body cavity. 



Each ovariole 2 consists of a double-walled, 

 blind tube divided into two distinctly marked 

 portions. The upper, filamentous 

 part originates as a blind tube 

 in the terminal cord of the ovary 

 and extends with a gradual in- 

 crease in size to the upper end 

 of the lower or follicular part, 

 which is funnel-shaped. The 

 size of this terminal, filamentous 

 portion or germarium, as I shall hereafter designate it, varies in cross- 

 section from I2.5(i to 5.6 [z. The follicular portion.or more properly speaking 

 the vitcllarium, begins with this funnel-shaped enlargement and extends to its insertion 



1 According to Lubbock (28) they are 8-10 in number. structural details of the egg-producing and egg-maturing or- 



2 Having doubts as to the truth of several points in the gan of insects. With this object in view I have studied with 

 theories advanced by Balfour (1), Brandt (9), Gegenbaur especial care the ovariole in Oecanthus niveus, Acheta abbre- 

 (20) and Ludwig (20), I wished to satisfy myself as to the viata, Periplaneta sp., and Acridium sp. These lour forms 



A. Fig. 1. B. 



Fig. 1. A. Female sexual organs, a. ovaries, b. recepta- 

 culum semi.iis; c. marks the beginning of tlie terminal filament; 

 d. that of the terminal ligament; c. ghindula appendicular is; 

 f. oviduct; g. vagina ; h. anal stylets; i. ovipositor. Magnified 

 25 diameters. (From nature and after L. Dufour.) 



Pig. 1. R. An ovary with the peritoneal and the connective- 

 tissue coverings removed and the ovarioles separated. ". ter- 

 minal filament of the ovariole (Endfaden); b. ovariole; c. oviduct. 



Fig. 1. C. Male sexual organs. (■ almond-shaped testicle; 

 v. d. vasa defferentia; v. s., vesiculae seminales; s. anal stylets. 

 (After Dufour.) 



