264 RESEARCHES ON FUNGI 



illegitimate combinations, e.g. (AB) X {Ab)^{aB) and (^6) X 

 {AB)-{-{ab), diploidisation of the haploid mycelium by the diploid 

 mycehum (as judged by the development of clamp-connexions on 

 the haploid mycehum and in one instance by the sex-factor analysis 

 of the clamp-connexion-bearing mycehum) often, if not always, 

 takes place ; but, it was pointed out that the exact explanation 

 of the diploidisation of a haploid mycelium in an illegitimate 

 combination of a haploid mycehum and a diploid mycelium must 

 await further investigation. 



While, as yet, in Coprinus lagopus, in all so-called illegitimate 

 combinations of haploid and diploid myceha, when the diploid 

 mycehum diploidises the haploid mycelium it still remains to be 

 determined whether or not the diploidisation process is normal in 

 the sense that each diploidised cell comes to contain two nuclei 

 of opposite sex {AB)+{ab) or {Ab)->r{aB), we are justified in affirm- 

 ing that in all so-called legitimate combinations of haploid and 

 diploid myceha, namely, the following : 



(AB) X {AB) + {ab), 

 (ab) X {AB)+{ab), 

 (Ab) X {Ab) + {aB), 

 {aB) X {Ab) + {aB), 



the diploidisation of the haploid mycehum is effected as normally, 

 smoothly, and rapidly as it is in the so-called legitimate combinations 

 of two haploid mycelia : 



(AB) X {ab), 

 {Ab) X {aB). 



This being so, we must admit that, under natural conditions, in 

 Coprinus lagopus (and probably in the Hymenomycetes generally) 

 there are two kinds of normal matings : (1) between two haploid 

 mycelia of opposite sex ; and (2) between a diploid mycehum and 

 an appropriate haploid mycelium. The first of these two kinds of 

 matings resembles in principle the mating of two haploid gametes 

 in animals and most plants, while the second finds no parallel in 

 animals and most plants. In no animal or plant does a fertilised 

 egg fertilise an unfertihsed egg. 



The fact that, in legitimate combinations of a haploid mycehum 



