Vol. XXIX August, 1915. No. 2 



BIOLOGICAL BULLETIN 



SEXUAL REACTIONS BETWEEN HERMAPHRODITIC 

 AND DKECIOUS MUCORS. 1 



ALBERT FRANCIS BLAKESLEE. 

 CONNECTICUT AGRICULTURAL COLLEGE, STORRS, Coxx. 



INTRODUCTION. 



Conjugation among the Mucors has been assumed to repre- 

 sent the simplest type of reproduction acknowledgedly sexual 

 in character. Some even have denied the term sexual to the 

 union of morphologically similar gametes such as occur in this 

 group. The present article will present further evidence in 

 favor of the author's contention that although the process is 

 morphologically a simple one, conjugation in the Mucors is as 

 definitely a sexual process as the morphologically more complex 

 type of reproduction in higher forms and that the sexes seem 

 even more sharply distinct. 



It has been shown by the writer ('04, '09) that the majority 

 of the forms among the Mucors are dioecious, with the sexes 

 separated in male and female races which are capable of being 

 propagated apparently to an indefinite number of vegetative 

 generations by means of nonsexual spores formed in sporangia. 

 In all the dioecious species carefully investigated the opposite 

 gametes, which are produced and unite to form zygospores 

 when the two sexual races of a given form are grown together, 

 do not appear to differ morphologically. Lacking a definite 

 criterion which an inequality of the gametes would have afforded, 

 the writer has provisionally designated the opposite sexes in 

 these forms by the signs ( + ) and ( ) on account of a generally 

 greater vegetative luxuriance of one sex over the other. That 



1 Report of investigation carried on, 1912-13, at the Carnegie Station for 

 Experimental Evolution, Cold Spring Harbor, N. Y. 



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