MAUPAS'S EESEARCHES ON OILIATE INFUSOBIANS. 611 



sessed as a primordial attribute an unlimited power of growth 

 and reproduction, as inherent as energy is in matter, and 

 quite independent of the actual mode of reproduction, sexual 

 or asexual. 



This latter part of Weismann's theory is completely over- 

 turned, so far as the Ciliata are concerned, by Maupas^s proof 

 of the existence of senescence and death as the normal ter- 

 mination of every cycle, when the possibility of normal conju- 

 gation is excluded. Thus the hypothesis of the essential 

 immortality of the Protozoa has lost its foundation in fact.^ 



Maupas^s own conclusion as to the real explanation is, that 

 fertilisation determines rejuvenescence, a view enunciated 

 by Biitschli and Engelmann, and adopted by Hensen and E, 

 van Beneden. 



Fertilisation is, in its essence, independent of sexual dififer- 

 entiation. This is clearly shown by the above studies on the 

 Ciliata, where both gametes and pronuclei are clearly identical. 

 Henceforward we can only look on sex as a secondary adapta- 

 tion to facilitate the act of fecundation. 



Besides rejuvenescence, fecundation does determine the 

 transmission of inherited qualities ; and we must admit this 

 part of Weismann's view : that it plays an important part 

 in variability. 



What is the essence of this act of fecundation considered 

 as a general phenomenon of organic life ? Maupas answers 

 this question in the following theses : 



1. Morphologically it is essentially a nuclear phenomenon. 



2. The nuclei retain their existence throughout ; Haeckel 

 was mistaken in assuming their disappearance in a " moneran 

 stage.'' 



3. A preliminary reduction takes place in the nuclear sub- 

 stance, which by successive normal mitoses is reduced by 

 three fourths; the parts so eliminated disappear by absorption 

 as " noyaux de rebut," or else are expelled as polar bodies. 



» My owu standpoint is somewhat different, for I admit the existence of 

 primitive forms, like the Monadina of Cienkowski, that are completely 

 agamous and " immortal." 



