Prof. E. Claparede.OTi the Heprodudion of the Aphides. 361 



of it, since lie does uot mention it in a subsequent, more de- 

 tailed paper*. The differences between these two observers 

 have become still more striking? since the publication of a 

 very elaborate memoir by ^I. Mccznikowf, accompanied by 

 more than fifty figures relating to the embryogeny of the 

 Jphides, and which is only the development of the note already 

 cited. 



On examining the publications to which I have just referred, 

 it is easy to see that both M. Mecznikow and M. Balbiani have 

 very conscientiously studied the objects that they had before 

 them, and that in most cases they have seen exactly the same 

 things. And yet what a distance there is between the final 

 results at which they have arrived ! A single word will suffice 

 to make this intelligible : with M. Mecznikow the Aphides are 

 agamogenetic j with M. Balbiani they are hermaphrodites. 



How are we to choose between these opposite results, an- 

 nounced by observers apparently equally conscientious ? The 

 only way is evidently to take up the subject again ah ovo, and 

 to submit all the divergencies to the touchstone of new and im- 

 partial observations. 



This is what I determined to do by an investigation of Aphis 

 Rosce, of which the embryos are comparatively favourable for 

 researches of this nature. The theory of the hermaphroditism 

 of the Aphides is untenable. Its author, founding his opinion 

 upon certain facts carefully observed, has evidently allowed him- 

 self to be carried far beyond the conclusions to which they 

 could legitimately give rise. His meeting by chance with certain 

 morbid phenomena has also perhaps assisted to keep him in the 

 track into which he had strayed. I do not hesitate to assert 

 that any one who will have the patience to resume carefully this 

 minute investigation will be compelled, while rendering justice 

 to the labours of M. Balbiani, to reject completely the conse- 

 quences which that author has drawn from them. 



The problem of the rcj^roduction of the y^^;/f?W<?5 is very simply 

 solved, according to ^I. Balbiani, in the following manner : — 

 From the first moments of embryonic life the blastoderm gives 

 origin to two juxtaposed cellular masses, one colourless, the 

 other permeated by granulations which give it a green or 

 greenish-yellow tinge. Of these two masses the first becomes 

 an ovary, and the second a testis, in which arc developed zoo- 

 spermia in the form of Ama'bce. These zoospermia fecundate 

 the ovary, the testis itself disaj)pears, and the fecundated ovules 



* Journal de I'Anat. ct tie la Phvsiol. 3** Annec, No. 5, September and 

 October 18GG. 



t " Embr>ologische Studien an Insekteu. Die Entwickelung dcr vivi- 

 paren Aphiden," Zeitsclir. fiir wi«8. Zool. xvi. p. 437. 



