GENERATION OF INSECTS. 403 



opening outwardly beneath the vulva (g). This latter canal gives 

 off, by the way, a narrow convoluted lateral canal, wliicli opens into 

 the vagina near the orifice of the spermatheca, and thus effects the 

 communication between the copulative sac and that reservoir. 



Experiment has proved the office of the spermatheca to be that 

 which its name implies. By the application of the fluid contained 

 in it to the eggs of an unimpregnated female, Hunter * made them 

 fruitful : he also found that the intromittent organ penetrated its 

 canal, — an observation which has since been confirmed by Audouin 

 and other observers. 



In the Hymenoptera the ovaria present great diversity as to the 

 number of the egg-tubes, which varies from 3 or 4 in the humble- 

 bee, to 6 in the wasp, to 10 in Pimpla^ up to more than 100 in the 

 queen-bee. f To the short canal of the sperm-reservoir there are 

 always attached tubular and glandular appendages, which usually 

 bifurcate and open into the duct of the reservoir. There is no bursa 

 copulatrix in the Hymenoptera. The colleterium is metamorphosed 

 into the poison-bag and glands ; unless, indeed, we may view the 

 appendages to the sperm-reservoir as homologues, and not merely as 

 analogues, of the coUeteria in other insects. 



With regard to the hemipterous modifications of the female organs, 

 I shall first refer, as in the case of the male organs, to the Aphis. 

 The two kinds of fertile females of this remarkable genus present 

 two modifications of the female organs. 



The viviparous females have two ovaria ; from each of these, four 

 multilocular oviducts are continued. The vagina is devoid of all 

 appendages. The eight oviducts are similar in size, and the embryo 

 is contained in the lowest or hindmost chamber. 



The oviparous females have, also, two ovaria with eight oviducts, 

 divided into two chambers each. The oviducts are seen in the most 

 different stages of development, so that usually not one of the eight 

 resembles another. In the fullest developed tube, the last chamber 

 is capacious, large, and oval ; the upper one small and conical. In 

 the undeveloped state, the whole tube forms only a simple pyriform 

 swelling of the oviduct, from which the upper conical compartment 

 is by degrees established. The lower chamber contains a finely 

 granular mass, which is gradually transformed into an oval egg ; the 

 upper chamber is full of cells, containing smaller nucleated cells. If 

 we regard these nucleated cells as germ-cells, we may conclude that 



* X. vol. iv. p. 113—116. CCXLVII. p. 175. 



t X, vol. iv. p. 117—119; Preps. 2609—2638. 



D D 2 



