448 THE INSECTA, § 348. 



the anus. This duct has several double or single appendages, of which 

 one with the females serves as a seminal receptacle (Receptaculum seminis), 

 or as a copulatory organ (Bursa copulatrix), while the others, in both 

 sexes, are true secretory organs. The vagina is often prolonged into a 

 horny ovipositor, and this same organ modified, with the males, is the Penis. 



The Eggs of Insecta are very varied in their forms and colors. Exter- 

 nally, they are frequently marked by prominences and raised lines, forming 

 a very varied, and often a very elegant design.'''' Those of some Cynipi- 

 dae, Ichneumonidae, and Siricidae, have one of their ends prolonged into a 

 long, straight or curved thread.^''' With some Hydrocorisae they are oblong 

 and their posterior extremity is covered with long, stiff bristles.'"' They 

 have, usually, a very solid chorion, and a thin vitelline membrane. The 

 vitellus is composed of fat-vesicles more or less colored, which communicate 

 their color to the entire egg. The germinative vesicle contains a germina- 

 tive dot which is often composed of several parts. <"''> 



These eggs are formed after two different types. 



1. With the Orthoptera, and various Coleoptera, the germinative vesicle 

 is formed in the posterior extremity of the tubular ovaries, and is gradu- 

 ally surrounded by a mass of granular vitelline substance. This vitelline 

 mass continues to increase until, at last, there is formed on its surface a 

 chorion, at first soft, but which finally becomes solid. During the course 

 of this development, the eggs succeed each other in a row, and in this way 

 advance towards the opening of the ovarian tube.'^' 



2. With the Lepidoptera, Diptera, Hymenoptera, Neuroptera, Cicindeli- 

 dae, Carabidae, and Hydrocanthari, the mode of formation is wholly diflFer- 

 ent. The vitelline mass which is disposed around the germinative vesicle, 

 increases in the following manner : Between each two vitelline masses, 

 there appear a group of large vitelline cells whose contents are blended 

 with the subjacent vitelline mass; while, the chorion is developed from a 

 layer of vitelline cells, commencing by its inner portion. It gradually 

 extends over the vitelline mass and cells, and finally, when the vitellus has 

 reached a certain volume, closes at the upper portion of this last. The 

 epoch at which the eggs reach their maturity coincides, with the Lepidop- 

 tera, Tipulidae, and Ephemeridae, with the end of their pupa state, so that 

 these insects are able to deposit their eggs as soon as they have cast off 

 their pupa envelope ; while, with the Libellulidae, the Locustidae, and 

 especially the Apidae, the eggs are not matured in the ovaries until a long 

 time after. ^^^^ 



With all Insecta, the sperm contains very active filiform spermatic 

 particles which become immediately stiff and looped when put in water. 

 These particles are developed in large cells whose involucrum finally dis- 



5 Kirby and Spence (Einleitung, &c., p. 100, Taf. 8 See Wagner, Prodromus, &c., p. 9, Tab. II. 

 XV.) have figured a great number of eggsof insects of fig. 18-22. 



various forms. See, also, Burmeister, Ilandb. &c. i* See Wagner, Abhandl. d. physical, mathemat 



Taf. I. and Lacordaire, Introduction, &c., PI. I. Klasse. der Akad. zu Munich, II. 1837, p. 554, 



6 See L. Dufour, Recherch. sur les Orthopt. fig. Taf. II. fig. 1 {Agrion), and Stein, Vergl. Anat. 

 128, 1-19 (Ci/iiips and Xiphydria) ; Hartig, in u. Physiol, d. Insekt. I. p. 47, Taf. IX. tig. 4, 8 

 Wiegmann's Arch. 1837, 1, p. 151, Taf. IV. {Try- {Telephorus and Acheta). 



phon, Paniscus, and other Ichneumonidae), and 1" Herold was tlie first who observed this re- 

 in Ge.rmar^s Zeitsch. f. Entom. p. 327, Taf. I. fig. markable mode of tlie formation of tlie eggs with 

 5, 6 (Cynips). tlie Lepidoptera ; see his Disquisit. &c. Tab. I. fig. 



7 The eggs of Ranatra have two long bristles ; 11-18, or Ann. d. Sc. Nat. XII. 1839, p. 195, PI. 

 while, with those of Nepa, these last form a coro- VII. fig. 13-18. Researches even still more de- 

 net ; see Roesel, Insektenbelust. III. Taf. XXII. tailed have been made by Stein, Vergl. Anat. &c. 

 XXIII., and L. Dufour, Recherch. sur les He- p. 52, Taf. IX. fig. 2, 9, 13 {Pontia and Pterosti- 

 inipt. PI. XVI. cAus). 



