74 THE PSYCHIC LIFE 



manoeuvering the animalcula go through before aban- 

 doning themselves to copulation; the movements they 

 execute admit of exact comparison with the actions 

 attendant upon copulation among higher animals. But 

 we shall recur further on to the physiological signifi- 

 cance of conjugation, when we shall endeavor to ex- 

 plain, according to the most recent investigations, the 

 function of the nucleus in the cellule. 



The question may be asked, what is the starting- 

 point, the provocative of these sexual phenomena, the 

 cause that sets them in play. Biitschli justly thinks, 

 that conjugation is determined by internal causes; in 

 fact, it takes place directly after very active periods of 

 spontaneous division, as Balbiani has shown. When 

 we bear in mind that the object of conjugation is to 

 replace the old nucleus which has become wasted and 

 worn out, we may conjecture with some degree of like- 

 lihood that the physiological condition of the nucleus 

 constitutes the sexual excitant that causes the Infuso- 

 ria to copulate. 



However that may be, a curious observation witn 

 the Paramacium aurelia has made us acquainted with 

 one of the structural conditions of the sexual instinct 

 in that Infusory. For a long time J. Muller had pointed 

 to the presence of filaments in the nucleus and even 

 nucleolus of Paramaecia, that had the appearance of 

 spermatozoids. Observations to the same effect have 

 increased since then, and it is now known that the 

 filaments are Schizomycetes, parasitic Bacilli, which 

 find their way into the nucleus and nucleolus, and mul- 

 tiply, after their customary mode of segmentation, by 

 disarticulation. Balbiani has definitely determined 

 the nature of these filaments by morphological and 

 micro-chemical methods; he has found out, among 



