Mycologisches Centralblatt, Bd. II, Heft 5. 
Ausgegeben am 17. April 1913. 
Conjugation in the hétérogamie genus 
Zygorhynchus. 
By 
A. F. BLAKESLEE, 
Carnegie Station for Experimental Evolution, Cold Spring Harbor, N. Y. 
(With 2 plates.) 
As is well known, sexual reproduction in the Mucorineae is brought 
about by the union of gametes cut off from hyphae which have met and 
swollen at their points of contact. In most of the forms investigated, 
these gametes are morphologically essentially equal. In a few herma¬ 
phroditic genera, however, there is a marked and constant difference in 
size between the gametes which unite to form the zygospore. Judging 
from the conditions in higher forms, the larger gamete in these mucors 
has been considered the female and the smaller the male. Zygorhynchus 
is the best known form of these hétérogamie species and its method of 
conjugation has been found by the writer as well as by most students of 
the group, to be in general the same as that characteristic of other mucors 
except for the difference between the gametes. Recently, however, Gruber l ) 
and also Atkinson 2 ) have called in question the usual account of of the 
process of conjugation in Zygorhynchus. Since their observations are at 
variance each with the other as well as with those of the writer it seemed 
desirable to make a careful restudy of conjugation in Zygorhynchus , 
especially in view of the fact that hétérogamie species have been made 
the basis of a paper on conjugation now in process of publication. 
- I 
1) E. Gruber, Einige Beobachtungen über den Befruchtungsvorgang 
bei Zygorhynchus Moelleri (Ber. d. Deutsch. Bot. Gesellsch. 1912, 30, 126—133). 
2) G. F. Atkinson, The Morphology of Zygorhynchus and its Relation 
to the Ascomycètes (Science N. S. 1912, 25 [26. Jan.], 151). — A letter to the 
writer from Prof. Atkinson outlines the results of his more recent study of Zygor¬ 
hynchus as follows: “Studies on the cytology of conjugation in Zygorhynchris hetero- 
gamus and Z. Moelleri by the aid of microtome sections, during the past year and 
which are still in progress have convinced me that I was in error in my interpretation 
of the sexual process in Zygorhynchus published in a note in Science N. S. 1912. 
This note was to the effect that the sexual apparatus was similar to that of Monascus, 
a female branch with a trichogyne in conjugation with a male branch I was led to 
this interpretation because of the fact that the female branch, in the form of Z. 
Moelleri which I studied usually, and in Z. heterogamus often, applies its tip to the 
side of the male branch before any outgrowth or sign of a gamete appears on the 
latter. I have now found that in such cases the small male gamete grows out from 
the male branch after contact and pushes the female branch away. I wish therefore 
to retract the interpretation of the sexual apparatus of Zygorhynchus given by me in 
the note above referred to.“ 
Mycologisches Centralblatt, Bd. II. 
16 
