612 



ZOOLOGY 



SECT. 



pen 



^yk 



blast 



with muscular walls opening on the exterior immediately below 

 the anus. Around the genital aperture are a series of chitinous 

 processes, the gonapophyses, which subserve copulation. 



In the female there are two groups of ovarian tubes or ovarioles, 

 each group or ovary (Fig. 508, ov.) consisting of eight. The 

 ovarioles of each group are united together anteriorly, where they 



are connected by a ligament to 

 the dorsal body-wall. Pos- 

 teriorly each group is connected 

 with a lateral oviduct (od.). 

 Each ovarian tube has a beaded 

 appearance, owing to its con- 

 taining a row of ova, which 

 increase in size posteriorly. The 

 two oviducts unite to open by 

 a median aperture on the 

 sternal surface of the eighth 

 segment of the abdomen. A 

 pair of unsymmetrical sacs 

 opening together in the middle 

 of the sternum of the ninth 

 segment constitute the sper- 

 mothcca or receptaculum seminis. 

 A pair of ramifying glandular 

 tubules, the colleterial glands 

 (coll. gld.), open behind the 

 spermotheca. A series of chitin- 

 ous gonapophyses, which aid in 

 carrying the eggs, are situated 

 .between the female genital 

 aperture and the anus. 



Development. - The eggs 

 are enclosed about sixteen 

 together in chitinous capsules, 

 the substance of which is 

 secreted by the colleterial 

 glands. They are laterally 

 compressed, concave on one 

 side (the future ventral side), 

 convex on the other (the future 

 dorsal side). 



The mature egg in the lower part of the ovary is enclosed in a 

 follicle composed of a single layer of cells, within which is the thin 

 chitinoid egg-shell or chorion perforated by a number of micropylar 

 apertures. After the processes of maturation and fertilisation, the 

 segmentation-nucleus undergoes division, the result being the 

 formation of a number of irregular amoeboid cells, which are 



D 



Wast 



.c 



FIG. 509. A -D, successive stages in the seg- 

 mentation of the ovum of an Insect ; blast. 

 blastoderm ; peri, peripheral protoplasm ; seg. 

 segmentation cells ; yk. yolk ; yk. c. yolk-cells. 

 (From Korschelt and Heider, after Bloch- 

 mann.) 



