DEVELOPMENT OF THE GENERATIVE ORGANS. 685 



the dorsal region on either side of the median line at a very 

 early period of development, in the form of a pair of minute 

 pyriform or reniform corpuscles composed of embryonic cells, 

 each of which is connected with the hypodermis, on the ventral 

 surface in front of the eighth abdominal segment, by a long fine 

 cellular cord, the genital cord. Herold [140] and Suckow [339] 

 discovered the differentiated rudiments of the sexual glands 

 in the caterpillars of the Lepidoptera ; and Herold found dis- 

 tinctly differentiated ovaries or testes in caterpillars which had 

 only escaped from the egg a few hours, and concluded from 

 this that the organs must be present in the embryo. Suckow 

 [339] states that he actually saw the gonads in the embryo 

 stage of Bombyx pini by the aid of a lens (?). He says ' The 

 first appearance of the sexual organs is, in the earliest stage 

 of embryonic life, as a bud from the alimentary canal, which 

 at a later stage is divided into two lateral halves by a fissure 

 extending from the alimentary canal and forms two hollow 

 threads. Towards the latter end of embryonic life the rudi- 

 ment of the sexual organ is separated from the alimentary 

 canal as a bulb at the anterior end of the two threads.' These 

 observations of Suckow's are exceedingly imperfect, and do 

 not agree with more recent investigations ; he evidently mis- 

 took the rudiments of the oviducts and bursa for the sexual 

 organs, and his description of these is inaccurate. 



Brandt [330] rejected Suckow's views as erroneous, and says 



349. KORSCHELT, E., ' Ueber einige interessante Vorgange bei der Bildung 

 der Insecteneiern.' Zeitsch. f. w. Zoo!., Bd. xlv., 1887. 



350. HENKING, H., ' Die ersten Entwicklungsvorgange in Fliegenei und 

 freie Kernbildung.' Zeitsch. f. w. Zool, Bd. xlvi., 1888. 



351. JACKSON, W. HATCHETT, ' Studies in the Morphology of the Lepi- 

 doptera.' Trans. Linn. Soc., Lond., vol. v., 1890. 



352. RITTER, R. VON, 'Die Entwickelung der Geschlechtsorgane und des 

 Darmes bei Chironomus.' Zeitsch. f. w. Zool., Bd. 1., 1890. 



353. POULTON, E. B., ' The External Morphology of the Lepidopterous 

 Pupa, its relation to that of other stages, and to the origin and history 

 of Metamorphosis.' Trans. Linn. Soc., Lond., vol. v., 1890-1891. 



354. HEYMONS, R., ' Die Entwicklung der weiblichen Geschlechtsorgane 

 von Phyllodromia (Blatta) Germanica.' Zeitsch. f. w. Zool., Bd. liii., 

 1891. 



