Vd^L M. Balbiani on the Reproduction 



IODINE. 



Dr. Nylander says (/. c), "D. Fries affert me reactionem iodo 

 efFectam attulisse tanquam signum Lichenes oinnino a Eungis 

 distinguens, etsi earn nunquam aliter eo respectu proposui quam 

 sicut adminiculum aecedens in certis casibus, ubi dubium re- 

 stitit in formis Lichenaceis infimis a Fungis simillimis distin- 

 guendis." 



XVIII. — On the Reproduction and Embryogeny 0/ Me Aphides, 

 (Third Note.) By M. Balbiani^. 



Having described in my two previous communications the phe- 

 nomena presented by the viviparous Aphides in their reproduc- 

 tion and development, I now come to the examination of the 

 same facts in the oviparous Aphides, which represent the last 

 generation produced by the preceding individuals towards the 

 close of the year. This autumnal generation consists, as is well 

 known, of males and females, which copulate, when the females 

 lay eggs which pass through the winter and are hatched only in 

 the following spring. 



The oviparous Aphides are produced under conditions exactly 

 similar to those which governed the development of the vivi- 

 parous forms. Not only does the embryo originate in an ovule 

 diflPering in no respect from that producing the latter, but all 

 that I have said with regard to the first modifications of the 

 ovum, the formation of the blastoderm and embryos, and the 

 production of the male and female generative elements is per- 

 fectly applicable to them. From this it results that these ani- 

 mals, which, after their birth, will give the most manifest signs 

 of the separation of the sexes, appear during a great part of 

 their embryonic existence like truly hermaphrodite creatures, 

 which it would be impossible to distinguish from their oviparous 

 [? viviparous] congeners. It is only when their development 

 has become considerably advanced that the first tendency to the 

 separation of the sexes is manifested. How this separation is 

 brought about, is what we shall now proceed to examine. 



Of all the means at the command of nature for the attainment 

 of this end, the most simple would evidently be to affect with 

 atrophy one of the sexual apparatus, the other continuing its 

 normal development. But this is not what takes place. The 

 male apparatus does not disappear, and is found, after birth, in 

 individuals of both sexes, with characters scarcely differing from 



* Translated from the ' Comptes Rendus,' June 25th, 1866, pp. 1390- 

 1394. See Annals, ser. 3. vol. xviii. pp. 62-69. 



