356 SYDNEY J. HICKSON. 



throws some light on the phenomenon of the conjugation of 

 the meganuclei in the Infusoria, a phenomenon which has no 

 parallel in the Metazoa. 



In the recent discovery of the phenomenon called "Xenia" 

 by the botanists in plants, we find a parallel although not 

 strictly homologous case. The ripe ovum of the angiosperm 

 is not an isolated cell. Its germinal cytoplasm is continuous 

 with the general cytoplasm of the embryo sac, in just the 

 same way as, according to my views, the germinal cytoplasm 

 of a Dendrocometes is in continuity with the somatic cyto- 

 plasm. It is quite possible, therefore, that anything which 

 influences the polar nuclei or the general cytoplasm of the 

 embryo sac would influence also the ovum (oosphere) before 

 or after fertilisation is effected. Nawaschin and Guignard 

 (7) have shown that in Lilium and some other Angiosperms 

 the second nucleus of the pollen grain does pass down the 

 tube, and conjugates with one of the polar nuclei to form the 

 mother nucleus of the endosperm nuclei. The second nucleus 

 of the pollen grain and the polar nuclei of the embryo may 

 be compared with the meganuclei of the Heterokaryote body. 

 Like these nuclei they conjugate at the time of the true sexual 

 conjugation of the germinal nuclei, and, moreover, they do 

 not by subsequent division give rise to the nuclei of the new 

 individual. It is true that there are important differences 

 between the two cases. In the plant the conjugation of these 

 nuclei is not temporary as it is in Dendrocometes, but 

 permanent, and the product of the conjugation gives rise to a 

 considerable progeny of well-defined nuclei in the endosperm 

 befoi'e their history is closed. But such differences as these 

 are not surprising in organisms so widely separated as the 

 Infusorian and the Angiosperm plant. Detailed comparison 

 of the two phenomena would probably not be profitable, and 

 might, indeed, be misleading. All that the comparison can 

 do for us at present is to confirm the impression that the 

 temporary fusion of the meganuclei of Dendrocometes that 

 has just been described is an important and essential part of 

 the process of conjugation, and not an exceptional or accidental 



