684 THE GENERATIVE ORGANS. 



of my sections. Such cells are, however, very difficult to 

 identify in the general mass of granular material. 



Weismann [2] described the yelk of the newly-laid eggs of 

 the Blow-fly as consisting of oil droplets and granules of im- 

 measurable fineness suspended in a clear fluid, and was unable 

 to find any germinal vesicle, which he says ' had already dis- 

 appeared ' in recently impregnated eggs. (See Section 4, h. 

 of this chapter.) 



4. ON THE DEVELOPMENT OF THE INTERNAL GENERA- 

 TIVE ORGANS. 



a. The Earliest Appearance of the Gonads in the Embryo and Larva. 



The rudiments of the gonads, ovaries and testes are well 

 known to appear, in many insects, imbedded in the fat bodies in 



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340. CLAUS, C, ' Beobachtungen iiber die Bildung des Insectcneies." 

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341. M KTSCHNIK.OW, E., ' Ueber die Entwickelung der Cecidomyienlarven 

 aus dem Pseudovum.' Archiv. f. Naturgeschichte, 1865. 



342. LEUCKART, A., ' Die ungeschlechtliche Fortpflanzung der Cecido- 

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343. GANIN, M., 'Beitrage zur Erkenntniss der Entwicklungsgeschichte 

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346. Nrssi'.Ai'M, I., 'Zur Kntuicklungsgcschichtc der Ausfiihrungsg;in-e 

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'.2. 



347. I'.Ai.r.i AM, M. G., ' Contribution a PEtnde de la Formation des Organs 



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348. N '\v. X. v<>\, 'Welche Insecten Organe diirften honiolog den 

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