Significmice of Sex a^id Nuclear Fusions. Harold Wager. 309 



and which, simply on account of their stainin^^ properties, were 

 regarded as nuclei, the presence of true nuclei in the majority 

 of Fungi had not been established. 



De Bary remarks for example (1887, Comparative Morpho- 

 logy and Biology of the Fungi, etc.), "The satisfactory dis- 

 crimination of true nuclei from other small bodies contained in 

 the protoplasm, and like them perhaps rendered more distinct 

 by colouring reagents, is extremely difficult, and can only be 

 obtained after renewed investigation." The determination of 

 the nuclear natiu-e of these granules depends not on their stain- 

 able properties, but upon their structure and mode of division. 

 Where this is accompanied by mitosis the nuclear nature of any 

 given body is unmistakable. 



Evidence of mitotic nuclear division had been obtained in 

 1883 by Sadebeck in Asci of Exoascus, by Strasburger in 1884 

 in frichiafaUax, by Fisch in 1885 in Ascomycetes, and by Eidam 

 in 1887 in Basidioboliis. 



In 1889 I described the nuclei of Peronospora parasitica and 

 showed that they possessed a normal nuclear structure, nuclear 

 membrane, nuclear net-work and nucleolus, and further that 

 the process of division was karyokinetic in that chromosomes 

 were formed, a nuclear spindle produced, and the separation of 

 the chromosomes along the spindle to form two daughter nuclei. 

 The nuclei of Peronospora parasitica in fact differ in no essential 

 particular from the nuclei of higher plants and animals. 



Hartog in 1889 and 1895 saw some mitotic stages in Sapro- 

 legnia, Rosen in 1892 thought he had obtained some indications 

 of nuclear division in Basidiomycetes, but he mistook stages of 

 the resting nucleus for these, Gjurasin in 1893 described mitosis 

 in the nucleus of the ascus in Peziza vesiculosa, Lister in 1893 

 mitosis in Mycetozoa, Wager in 1891-4 mitosis in Basidio- 

 mycetes, in which spindle figure, equatorial plate and centro- 

 somes were seen, and Harper in 1895 obtained beautiful figures 

 of mitosis in asci. 



Since then our knowledge of the nuclei of Fungi has been 

 extended to all the groups of Fungi, and we know that the nuclei 

 of the Fungi do not differ in any essential feature from the 

 nuclei of higher plants and animals. 



Side by side with our knowledge of their nuclei our know- 

 ledge of the sexual phenomena in the Fungi has been developed 

 and the importance of the nuclei in the process has been 

 demonstrated. 



All that we know definitely of the behaviour of the nuclei in 

 the formation of the sexual organs and in the subsequent fer- 

 tilisation which takes place has been discovered during the last 

 thirty years, but all the essential features of this fertilisation were 



