THE REPRODUCTIVE SYSTEM. Ixi 



whilst lying within the vagina. See Plates V., XII., 

 XXXI., and XXXIV. 



Bnrmeister makes some interesting remarks on the 

 forms of the penis in Centrotus, &c., and in cases where 

 the ornamental projections on the pronotiim would seem 

 to interfere with the approach of the male. Union 

 here must take place whilst the insects are side by side, 

 and a curved penis accordingly he thinks may be 

 necessary (p. 218). 



Prof. Ellis Agar gives a remarkable account* of 

 the male parts of Cicada septendecem, with an illus- 

 tration. The external organ mainly consists of a 

 chitinous sheath, of about 0-25 inch in length, which 

 is traversed by a highly elastic tube. This tube can 

 be alternately everted and contracted, at will, within 

 the sheath, as it lies between the vaginal walls. The 

 spinous coat of the elastic tube he thinks may act, as 

 I have above noted, as a stimulating apparatus to the 

 female. When the hooks and claspers are locked 

 together, the sexes cannot hastily be separated without 

 mutilation, as Prof. Kiley has shown, and I have noted, 

 elsewhere. 



As to the female organs, the ovary is composed of 

 several chains of bilocular chambers, which spring 

 from a common centre. These chambers, which may 

 be as many as forty, develop the ova which pass from 

 time to time down the oviduct, and there meet the con- 

 tents of the spermatheca before they reach the vulva. 

 The opening is on the ninth somite, and is concealed 

 by two valves which enclose the complex ovipositor. 

 This last curious organ answers two purposes, viz., that 

 of a boring or [)loughing instrument, and, by the super- 

 position of the saws and rasp-like lamina3, that of a 

 channel to convey the eggs to the grooves cut by the 

 insect for their nidus. 



The anus, as in other insects, is placed above the 



■'■ See ' Jonrn, Trenton Nat. Hist. Soc.,' Pennsylvania, vol. i. Trans., 

 1887, p. 43. 



