264 CLASS vnr. 



where a single impregnation suffices for many families in succes- 

 sion ; the males are not observed until the end of summer or in 

 autumn ; they impregnate the last family, consisting of wingless 

 females, which without copulation would be barren. Their eggs 

 remain during the winter on branches of trees, and in spring 

 produce only female plant-lice which without copulation are prolific 

 and viviparous. BONNET, to whom we owe this discovery, found 

 that in the space of three months nine successive generations were 

 produced without copulation 1 . 



Amongst the Myriapoda the Chilopods have only a single ovary, 

 in form of a long sac situated beneath the intestine. In the 

 remaining Insects there are two ovaries. Sometimes they have the 

 same form of tubes or sacs (Forficula, Ephemera, Stratiomys) ; in 

 some flies the sac is very long, rolled spirally like a watch-spring, 

 and separated by many transverse partitions into cells 2 . In most 

 Insects each ovary consists of a number of tubes (games ovig^res 

 LEON DUFOUR). Sometimes these are situated around a sacciform 

 dilatation from which the oviduct arises (ovaria baccata), as in 

 Meloe L. and Lycus (coleoptera) 3 . Or these tubes are situated 

 lengthwise along the origin of oviduct (ovaria ramosa), as in 

 Cicada 4 ; sometimes on one side only, like the teeth of a comb, as 

 in PJiasma and Tenthredo (Athalia). But in by far the greatest 

 number of cases, these tubes are situated at the beginning of the 

 oviduct like the leaflets of a digitated leaf, at the end of a common 

 stalk (ovaria digitata, fasciculata). Such ovaries are seen in the 

 Lepidoptera, where each of them consists of four tubes. The 

 number of these tubes is however very different, not only in the 

 different orders, but even in the same order, and occasionally in the 

 same natural family ; whilst, ex. gr. Bombyx and Xylocopa (Hymen- 

 optera) have four, in the Honey-Bee are more than one hundred 5 . In 



1 C. BONNET, Traite dlnsectologie, i. Observations sur les Pucerons, Paris, 1845, 

 iamo. (Euvresi. 1771, Svo. DUVAU has obtained even eleven successive generations 

 without copulation; Ann. dcs Sc. nat. v. 1825, p. 224. There are also some examples 

 of the same phenomenon in insects of other orders. BURMEISTER, 1. 1. s. 336, 337. 



2 REAUMUR, Mem. pour servir a VHist. des Ins. IV. PI. -29, f. 7 and 8. 



3 BRANDT and KATZEBURG, Medizin. Zoologie n. Tab. xvu. fig. i k, Meloe vane- 

 gains, Tab. xix. figs, u, 15, Lytta vesicatoria ; LEON DUFOUR, Ann. des. Sc. nat. vi. 

 PI. 1 8, fig. i, Lycus rufipennis. 



4 LE"ON DUFOUR, Hemipteres, PL 17, fig. 189. 



5 LE"ON DUFOUR, Mem. pretends, Tom. vn. p. 408. According to SWAMMEBDAM, 



