OVARIES 



139 



JLtc 



female. The egg-tubes are connected with a duct for the con- 

 veyance of the eggs to the exterior, and the arrangements of 

 the tubes with regard to the oviduct also vary 

 much. An interesting condition is found in 

 Machilis (see Fig. 94, p. 188), where the' seven 

 egg - tubes are not arranged in a bunch, but 

 open at a distance from one another into the 

 elongated duct. The tw T o oviducts usually unite 

 into one chamber, called the azygos portion or 

 the uterus, near their termination. There are a 

 few Insects (Ephemeridae) in which the two ovi- 

 ducts do not unite, but have a pair of orifices at 

 the extremity of the body. Hatchett- Jackson 

 has recently shown a that in Vanessa io of the 

 Order Lepidoptera, the paired larval oviducts are 

 solid, and are fixed ventrally so as to represent 

 an Ephemeridean stage ; that the azygos system 

 of ducts and appended structures develop separ- 

 ately from the original oviducts, and that they 

 pass through stages represented in other Orders 

 of Insects to the stage peculiar to the Lepi- 

 doptera. Machilis, according to Oudemans, is a 

 complete connecting link between the Insects 

 with single and those with paired orifices. 



There are in different Insects more than one 

 kind of diverticula and accessory glands in con- 

 nexion with the oviducts or uterus ; a recepta- 

 culum seminis, also called spermatheca, is common. 

 In the Lepidoptera there is added a remarkable 

 structure, the bursa copulatrix, which is a pouch 

 connected by a tubular isthmus with the common 

 portion of the oviduct, but having at the same time a separate 

 external orifice, so that there are two sexual orifices, the opening 

 of the bursa copulatrix being the lower or more anterior. The 

 organ called by Dufour in his various contributions glande sdbifique, 

 is now considered to be, in some cases at any rate, a spermatheca. 

 The special functions of the accessory glands are still very 

 obscure. 



The ovaries of the female are replaced in the male by a pair 

 1 Tr. Linn. Soc. London, 2nd ser. ; Zool. v. 1890, p. 173. 



FIG. 75. Egg- tube 

 of Dytiscus nar- 

 ginalis ; e.c, egg- 

 chamber ; n.c, 

 nutriment cham- 

 ber ; t.c, terminal 



. chamber ; t.t, 

 terminal thread. 

 (After Kor- 

 schelt. ) 



