44 Fraser. — Contributions to the Cytology of 
continue its growth, and it has been ascertained to give rise to other asci. 
I am inclined to think that the formation of the ascus from the subterminal 
cell of the ascogenous hypha is nothing more than a provision to allow the 
further growth of the latter, the asci developing, as is well shown in Fig. 13, 
and in Faull’s Fig. 75, as lateral branches of the hypha. Probably the 
conjugate division of the two terminal nuclei of the ascogenous hypha, is 
a convenient method of providing two nuclei in the ascus and one in the 
terminal cell which is to continue its growth, rather than an arrangement to 
prevent the near relationship of the ascus nuclei. Where a cell contains 
more than one nucleus, simultaneous division seems to be the rule ; it 
occurs, for instance, in the oogonium of the Oomycetes, in the embryo-sac 
of Phanerogams, and in the ascus itself. 
The development of the ascus has been shown to be liable to con- 
siderable variation, the only constant process being the inclusion and 
subsequent fusion of two nuclei ; even this is subject to exception, since in 
H. rutilans young trinucleate and tetranucleate asci are found. 
The fusion in the ascus is regarded by Dangeard (12, 13) as sexual, 
and he has consistently denied the occurrence of a fertilization at any other 
stage in the life history of the Ascomycetes. 
Recent research, however, has proved that, in a number of cases, 
a typical or reduced fertilization precedes the formation of the ascogenous 
hyphae. This in itself, unless the occurrence of two fertilizations in a single 
life history be regarded as possible, serves to disprove the sexual nature 
of the fusions in the ascus. In Humaria rutilans the fact that the reducing 
division begins before this fusion takes place, constitutes further evidence 
in the same direction. 
For Harper (31) the fusion in the ascus serves to adjust the nucleo- 
cytoplasmic equilibrium. This indeed would account for the presence of more 
than one nucleus, since the ascus is to become the largest cell of a typically 
multinucleate mycelium, but it does not appear to explain their fusion. 
In Humaria rutilans the nuclei lie in contact, and have entered on the 
prophases of division before fusion occurs. It may be suggested that, at 
this stage, the nuclear membrane becomes increasingly delicate, and the 
nuclei simply flow into each other, as is the case when nuclei artificially 
separated from their cytoplasm are brought into contact. 
The Meiotic Phase. 
Considerable additions to our knowledge of chromosome reduction 
among animals and higher plants have been made during recent years. 
In 1905, Allen (1) investigated the reducing division in Lilium cana- 
dense ; he described the approximation and fusion in pairs of chromatin 
strands in the early prophase of the heterotype division. Synapsis then 
takes place, and is followed by a uniform distribution of the spireme. 
