RATE OF MOVEMENT OF NUCLEI 213 



on one spot at their periphery when they were about 6 cm. in 

 diameter. The inoculations were as follows : 



(AB) with {AB)+{ab), 

 (AB) with (ab), 

 (ab) with {AB)^{ab), 

 (ab) with {AB). 



Again diploidisation of the large central haploid mycelium took 

 place in each combination ; and again its progress was relatively 

 slow. When growth of the mycelia on the plates came to an end, 

 diploidisation had just been completed in the two lower matings 

 listed above, but it had passed no more than half way around the 

 central mycehum in the two upper matings listed above. 



The slowness and incompleteness with which the central haploid 

 mycelia were diploidised in the experiments just described, as com- 

 pared with the relative rapidity and the completeness with which 

 diploidisation had been found to take place in similar experiments 

 described under (2) made two weeks earlier than the set of six 

 matings and six weeks earlier than the set of four matings here 

 treated of, strongly suggests that the results of matings are influenced 

 by age, in that older mycelia effect diploidisation or are diploidised 

 more slowly than younger mycelia that have not long been developed 

 from a germinating spore. 



The Rate of Movement of Nuclei through a Haploid Mycelium 

 which is being diploidised by (1) another Haploid Mycelium, or 

 by (2) a Diploid Mycelium. (1) Eight comparative ex2)eriments. 

 The haploid mycelia Nos. 5 and 10 used in the previous experiments, 

 on account of their having become sexually less vigorous through age, 

 were now discarded. A fresh set of spores was germinated and ten 

 new monosporous mycelia were thus obtained. These myceha were 

 paired with one another in all possible ways, with results embodied 

 in Table I. In this Table a ( +) sign indicates that clamp-connexions 

 were formed and a ( — ) sign that no clamp-connexions were formed. 

 The mycelia which behaved ahke have been set together. All the 

 four possible kinds of myceha were obtained and to them the 

 symbols (AB), (ab), (Ab), and (aB) have been assigned in the usual 

 manner. 



