iqiq] burger— CUNNINGH AMELIA 145 



The "neutrals" 4-6 and 15, however, formed zygospores when 

 contrasted with culture no. 9 in series C. Since 9 was proved in 

 series B to be plus, nos. 4-6 and 15 would therefore be considered 

 as minus. 



The neutral no. 11 formed normal zygospores when contrasted 

 with 3 in series F. We have shown, however, that 3 is plus in 

 series B and minus in series A; therefore no. 3 would have to be 

 considered hermaphroditic. 



Nos. 18, 19, 22, and 23, which were shown to be neutrals, 

 formed normal zygospores when contrasted with no. 10 in series 

 G. No. 10 was shown to be plus in series B; therefore nos. 18, 

 19, 22, and 23 must be considered as minus. If these numbers 

 are considered as minus, the question arises, why did they not 

 conjugate with nos. 34, 21, 9, 7, and 3, which were all shown to 

 be pfus ? 



The evidence that nos. 4-6, 11, 15, 18, 19, 22, 23, 27, 28, 30, 

 31, and 2)i are "neutral" does not seem to fit the accepted con- 

 ception of this term, for they are able to form normal zygospores 

 when contrasted with the strains whose gametes are compatible. 



If plus and minus strains of the Mucor V. are female and male 

 respectively, they should have shown a sexual reaction with 

 different strains of C. bertholletiae which were capable of forming 

 zygospores when contrasted with each other. This neutrality 

 cannot be explained on the grounds of loss of vitality; neither do 

 I believe this neutrality can be explained by Burgeff's hypoth- 

 esis, that there are the same number of plus and minus nuclei 

 in a given hypha, the plus nuclei annulling the zygotactic influence 

 of the minus. It has been shown that a strain which is neutral 

 to 2 strains, which themselves are plus and minus respectively, 

 has the power to conjugate with a third strain if their gametes 

 are compatible. The writer is unable at the present time to give 

 any satisfactory explanation of this pseudo-heterothallic condi- 

 tion in Cimninghamella bertholletiae, but it is evident that we 

 still have much to learn as to the sexual conditions in the 

 Mucorineae, especially in relation to so-called neutral strains. 



