PRESIDENT S ADDRESS. b / / 



The significance of these bodies in the phenomena of impregna- 

 tion has been universally recognised since the publication of Fol's* 

 brilliant observations, and Guignard's more recent discoveries 

 have proved that they play a precisely analogous part in the 

 fertilisation or lowering plants. f They have been fou.nd to occur 

 in the ova of a variety of animals from the earlie.st stages of their 

 development, and they have also been detected in the male sexual 

 cells, and recently in the spermatozoa themselves. Thus the view 

 that, as the spermatozoon is little more than a nucleus, the nucleus 

 must be all-important in reproduction and inheritance has been 

 gradually losing ground ; with the entry of the spermatozoon 

 there appears within the ovum not only the male pronucleus, but 

 also a male centi'osome which is in all probability derived from 

 the cytoplasmic part of the spermatozoon ; and this would appear 

 to take part equally with the male pronucleus in bringing about 

 fertilisation. Guignard's general conclusion from his observation 

 of the behaviour of these bodies in the fertilisation of plants is that 

 fecundation consists " not only in the copulation of two nuclei of 

 different sexual origin, but also in the fusion of two protoplasms 

 likewise of different origin represented essentially by the attrac. 

 tion-spheres of the male and female cells." 



On the other hand a good many observations and experiments 

 on the Protozoa seem to point to the importance of the nucleus in 

 that group in connection with the regeneration of lost parts. 

 But here we meet with apparent contradictions, for while BalbianiJ 

 states that regeneration takes place in Stentor only in the case of 

 portions that contain a part of the nucleus, Gruber§ finds that 

 when spontaneous fission has been once initiated, if a transverse 

 section be made so that none of the nucleus remains in the 



* "Die 'Centrenquadrille,' eine neue Episode aus der Befruchtungsge- 

 schichte." Anat. Anz. VI. (1891). 



t "Sur la nature morphologique du ph^nomfene de la f(5condation." 

 Comptes Rendus, T. 112, p. 1320. 



X Annales de Micrographie, iv. (1892). Abstract in the Journal of the 

 Royal Micros. Soc. Dec. 1892. 



§ " Ueber kiinstliche Theilung bei Infusorien." Biol. Centralbl iv, and v. 



