strasburger: fertilisation in phanerogams. 277 



It has already been stated that the division of the germ nucleus 

 gives rise to two daughter nuclei, in each of which there are as many 

 pieces of nuclear thread from the father as from the mother, and that 

 all the descendants of the germ nucleus carry a nuclear thread, one 

 half of which is of paternal and the other half of maternal origin. 

 These halves, likewise, must themselves be descended from the 

 grandfather and grandmother of the mother's or father's side, and 

 the latter part again from great-grand-parents and so on. Hence a 

 nuclear thread is in reality compounded of pieces descended from 

 various generations, the pieces being so much the smaller, the further 

 the generation to which they belong goes back. This composition 

 makes the nucleus specially suitable as a guardian of the specific 

 properties of the organism, and explains the complicated phenomena 

 which present themselves when the nucleus divides. 



This view of the composition and origin of the nuclear threads 

 leads our author to another conclusion, on which he insists somewhat 

 strongly, viz., that there is no functional difference between the two 

 cell-nuclei, which by their copulation complete the process of ferti- 

 lisation. This at first strikes one as a strange and indeed a startling 

 conclusion, but Strasburger states that no morphological facts are 

 known to him which the assumption of a functional difference in the 

 two nuclei would demand. The difference, he„ says, has been 

 assumed on the ground of physiological considerations only, but the 

 nuclei are not different in their nature, and are not sexually differen- 

 tiated in the sense in which the individuals from which they are derived 

 are so. All sexual differentiations, therefore, serve only the purpose 

 of bringing together the two cell-nuclei which are necessary for the 

 sexual act. 



As a final test by which his theory is to be tried, Strasburger 

 considers to what extent it is capable of explaining the phenomena 

 of hybridism. These phenomena, as most naturahsts are aware, are 

 peculiar, and by no means easy of explanation. In some hybrids 

 the characters of the male predominate ; in others the characters of 

 the female and in others again both are equally represented. In 

 explanation of this, Strasburger reminds his readers that the female 

 produces not only the egg-nucleus, but also the cytoplasma in which 

 it is embedded, and that in this cytoplasma, according to his theory, 

 the nutrition of the combined nuclear threads takes place. It is 

 therefore conceivable, he says, that the nutrition of the two threads 

 m.ay or may not be quite equal, and in the latter case the characters 

 of the more privileged one will predominate. The well-known 

 circumstance that the hybrids between A and B, and between B and 

 A (the first being regarded as the male), do not always agree in their 



July 1885. 



