OF MICR O- OR GANISMS. 75 



other things, that the filaments do not dissolve in 

 strongly concentrated alkaline solutions; and it is 

 known that Bacteria exhibit this peculiar attribute of 

 offering a great resistance to destructive agents. 



In the nucleus which they have penetrated, these 

 parasites induce a pathological condition that results 

 in destroying every manifestation of the sexual in- 

 stinct in this Infusory. Among a swarm of animals of 

 this species that are in copulation, single individuals 

 are found that show a nucleus and nucleolus corn- 

 completely charged with Bacteria; sometimes these 

 organs suffer an enormous dilatation, the nucleus be- 

 coming nothing more than an enveloping membrane 

 which is filled like a huge pouch with parasites. The 

 animal continues to live, but it no longer attempts to 

 copulate. 



VII. 



It is not our intention to make a full and complete 

 study of fecundation in higher animals and plants; 

 there is but one phase of that phenomenon that can 

 enter into a general study of Micro-organisms, and that 

 is the history of the sexual elements, of their form, 

 their movements, and lastly their copulation. 



We shall describe animal fecundation first, and 

 plant fecundation afterwards; regarding these phe- 

 nomena particularly from a psychological standpoint. 



Among metazoans, fecundation may be divided 

 into two distinct acts. The first, and most apparent, 

 consists of the union of the two individuals; of this we 

 shall not have to speak here; it is a phenomenon that 

 lies outside the limits of our investigations. The sec- 

 ond, more deep-seated, consists in the phenomena 



