Significance of Sex and Nuclear Fusions. Harold Wager. 311 



the fusion nucleus eight, and that the result of the reducing 

 division was the separation of these eight chromosomes into 

 two groups of four each for the two daughter nuclei. Maire's 

 statement that the vegetative nuclei contain only two chromo- 

 somes, and the fusion nucleus four, is quite incorrect. 



My original investigations gave some indications of the fusion 

 of three or four nuclei in the basidium, and Maire also stated 

 that he had found three or four nuclei in young basidia, but the 

 subsequent researches of Harper, Dangeard, Maire and myself 

 showed quite clearly that this was abnormal and that the 

 basidium normally contains two nuclei only. 



Concerning this discovery of two nuclei in the basidium, and 

 their subsequent fusion, Professor Harper remarks: "The most 

 striking discovery as to fusion in the fungi and the one which 

 preceded and led the way to very many of the most important 

 later results was the observation by Wager of paiied nuclei and 

 the subsequent fusion of these nuclei in the young basidium." 

 This was "the first proof of the existence of an endokaryogamy 

 — the fusion of nuclei not derived from separate and indepen- 

 dent gametes as in ordinary fertilisations, but having had a 

 similar if not identical history in the cells from which the 

 basidium arose. Such a process was entirely unknown before 

 in either plants or animals (American Naturalist, Sept. 1910). 



Subsequently in 1893 (Comptes rendus, Acad. des. Sc. Feb. 

 1893) Dangeard and Sappin-Trouffy announced the discovery 

 of a binucleate condition in the aecidiospores and teleutospores 

 of the Uredineae, and in Le Botaniste (ser. iv. 1894-5) Dangeard 

 announced the discovery of two nuclei in the ascus, and their 

 fusion. Dangeard regards the fusion of nuclei in the basidium, 

 ascus and teleutospore as sexual in the ordinary sense of the 

 term, the nuclei which fuse being equivalent to gametes, and 

 the resulting uninucleate cell in each case as equivalent to an 

 oospore or e^g. Harper's observations on the true sexual organs 

 of the Ascoraycetes, and the discovery of binucleate cells in the 

 vegetative stages of the Basidiomycetes and the cell fusion dis- 

 covered by Blackman at the base of the aecidium in the Ure- 

 dineae all tend to show however that the problem of the sexu- 

 ality of the higher Fungi is an extremely difficult one to solve. 



Whatever sexuality may be intrinsically, whatever may be 

 its function physiologically or in heredity, it is essentially 

 characterised by the association of two cells, each with its 

 nucleus, and their fusion to form a zygote. The production of 

 this zygote or e^^ takes place at a definite period in the life- 

 history of any plant or animal in which it occurs, marking the 

 close of a definite cycle in the life-history, and the beginning of 

 another. Within this egg are contained all the essential charac- 



