STRASEURGER : FERTILISATION OF PHANEROGAMS. 205 



Hence it is not the morphologically differentiated elements of the two 

 cell-nuclei, but the undifferentiated ones, that mutually penetrate one 

 another. For the nuclear sap, this must necessarily happen ; for the 

 nucleoli, the union may not take place, and consequently it cannot 

 be regarded as an essential part of the process of fertilisation. The 

 result of the act of copulation is the formation of a germ-nucleus 

 which contains the nuclear network of the two copulating nuclei. 

 Very soon this nucleus divides, and the division takes place in such 

 a way that each of the two daughter nuclei contain just as many 

 threads from the father (sperm-nucleus) as from the mother (egg- 

 nucleus). In the daughter nuclei, the segments of the nuclear threads 

 unite by their ends to form a single thread, which is therefore built 

 up partly from the father and partly from the mother. Hence the 

 blending of the nuclear threads of the two copulating nuclei first 

 occurs in the daughter nuclei formed by the division of the germ- 

 nucleus. As regards all succeeding generations of nuclei, Strasburger 

 seems to be of opinion that they contain nearly an equal number of 

 pieces of nuclear thread from the father and from the mother. 



In entering upon a critical examination of the process of 

 fertilisation, Strasburger proceeds on the assumption that the 

 essentials remain the same in the whole organic kingdom, and that, 

 consequently, the facts gained in the investigation of phanerogams 

 can be utiHsed to elucidate the process in other cases. Hence he 

 says we must assume that even in the simplest processes of 

 copulation, whether the bodies concerned are motile or stationary, as 

 in Fandori?ia and Spirogy?'a, the fertilisation depends upon the 

 blending of the cell-nuclei of the conjugating bodies. The fact that 

 in these cases both bring a nearly equal quantity of cytoplasma to 

 the zygote or zygospore he regards as a subordinate matter, and as 

 no indication that cytoplasma is necessary for the act of copulation. 

 This view is further confirmed by reference to Ftiais, where the egg 

 contains several hundred thousand times as much cytoplasma as the 

 spermatozoid, though both bodies contain equal quantities of nuclear 

 substance. In all cases, it would seem that the cell-nuclei destined 

 for the sexual act, must enter into a physiological condition necessary 

 for the purpose, and our author considers he has shown they can 

 only attain to this in consequence of a certain mode of nutrition. 

 Hence, the medium in which they find themselves — i.e. the surround- 

 ing cytoplasma — must embrace the conditions requisite for this, and 

 from it they must draw the nutriment which equips them for the 

 performance of their special functions. 



[To be cotitinued.) 



April 1885. 



