104 MM. A. Famintzin and J. Boranetsky on 



the nucleus and of the vacuole were gradually effaced and 

 finally disappeared entirely, whilst at the same time the entire 

 contents of the cellule became of a very fine, homogeneous 

 granular structure. Finally the membrane of the cellule became 

 torn, and the contents issued forth like a small circumscribed 

 sphere, and resembled a small cellule still attached to the 

 mother cell. The protuberance rapidly increased in size, and 

 soon attained the dimensions of the primitive cellule, so that 

 the contents became twice their original size. The cellule 

 was thus emptied and its contents transferred entirely into the 

 protuberance, which, as it gradually increased, assumed the 

 form of a sac. At this moment the division of the contents 

 into zoospores became evident, and we distinguished on its 

 surface a very thin membrane, which was speedily ruptured, 

 and through the aperture of which the zoospores issued one 

 after the other. Generally the membrane was speedily dis- 

 solved, but sometimes it remained intact for a long time after. 



The zoospores are elongated, narrowed at the anterior part, 

 and furnished at this end with two cilia directed forward. By 

 means of iodine, we could easily recognize in the middle of 

 each zoospore a nucleolate formation, the nature of which we 

 are unable to explain. The zoospores moved in the water for 

 a certain length of time, and then became motionless. We 

 are still unable to explain their ulterior development ; and all 

 our knowledge only establishes that the motionless zoospores 

 augment in size without any change of form, and finally attain 

 to two or three times their primitive diameter. 



The most delicate and at the same time most important 

 point of these researches was to establish incontestably that 

 the zoosporal cellules were really the gonimic cellules, and not 

 some other organism which had been accidentally developed 

 in our apparatus. We believe that the following facts demon- 

 strate this fully : — 



1. We obtained the zoospores by means of gonidia sown 

 on the surface of bits of bark previously boiled in water, and 

 consequently cleansed from living organisms. Direct observa- 

 tion has demonstrated, moreover, that our seed-beds did not 

 contain any other green organism besides the gonidia which 

 we had deposited in them, and that they were only polluted 

 by some filaments of a Ilyphomycetes which had probably been 

 transported on the bark or existed in the water in which the 

 lichen had been macerated. 



2. The changes which we have described were observed not 

 only in a very great number of free gonimic cellules, but also 

 in gonidia still attached to the medullary filaments. From 

 these latter we have repeatedly observed the zoospores to 



