52 
Fraser. — Contributions to the Cytology of 
the spores as delimited by the differentiation of a finely granular proto- 
plasm, and from Overton ( 37 ), who confirms the description of Harper. 
Fanils account is of great interest, but it does not seem to satisfactorily 
explain either the persistence of the astral rays or the formation of the 
nuclear beak ; the latter appears in H. rutilans , as in the forms described 
by Harper, before the spore is delimited. 
The exact function of the radiations from the centrosome is, owing to 
their extreme tenuity, somewhat difficult to ascertain in H. rutilans. 
Farmer and Moore ( 18 ) regard the spindle fibres rather as protoplasm 
modified by the forces at work in the cell than as actively growing entities. 
For them the spindle is a passive manifestation of the real operating agency. 
In H. rutilans , the spore is delimited by the astral rays, but it would 
seem that these represent not cell organs of the nature of cilia, as suggested 
by Harper ( 31 ), but rather currents set up in the neighbourhood of the 
centrosome as it pushes into the dense cytoplasm near the pole. It is 
in accordance with such a point of view that the boundary of the spore 
should sometimes be partly defined by the walls of neighbouring vacuoles, 
or, as would seem to be the case in the abnormal ascus of Fig. 55, by the 
ordinary cytoplasm. 
Summary. 
1. The ascocarp of Humaria rutilans originates as a tangle of septate 
hyphae ; sexual organs are not differentiated. 
2. Fusions of nuclei in pairs occur in the hypothecium constituting 
a process of reduced fertilization or apogamy. The cells containing the 
fusion nuclei form ascogenous hyphae. 
3. Divisions in these hyphae are karyokinetic, showing sixteen chromo- 
somes. 
4. The first and second divisions in the ascus are respectively heterotype 
and homotype. They show the stages observed by Farmer and Moore in 
the meiotic phase of certain animals and plants, and they bear the same 
interpretation. 
5. During the first mitosis fusion of the two nuclei in the ascus occurs. 
At this time the spireme in each already shows evidence of longitudinal fission. 
6 . Sixteen chromosomes appear in the first two divisions in the ascus 
and in the prophase of the third. They are regarded as representing two 
sets of post-meiotic chromosomes united with one membrane. 
7. In the telophase of the third division eight chromosomes only are 
seen at each pole. The two sets of post-meiotic chromosomes have thus 
separated, and the reduced number is apparent. To this type of reduction 
the name brachymeiosis is given. 
8. The spores are outlined by radiations passing from the centrosome ; 
near the base of the spore vacuoles may take part in the process. 
July , 1907. 
