Cytology of a new variety of A chly a americana. 163 
certainly been seen in all stages of karyokinesis. Figs. 60 to 
70, which, it should be noted, are somewhat diagrammatic, 
having been drawn by free hand and magnified 2,400 
diameters, illustrate the spirem-stage, which was very distinct, 
and spindles chiefly in metakinesis and diaster-stages. The 
four resting nuclei pressed closely together in Fig. 70, and 
which occurred near the apex of a germ tube are worthy 
of note. 
An endeavour was made to determine the number of 
chromosomes, but the success attending it was scarcely com- 
mensurate with the effort. The chromosomes are so small 
and so close together that positive determinations were not 
possible. The conviction, however, was forced upon me in 
several cases that the number seen in a side view of the 
spindle was four, double that seen in the gametangia. 
Provisionally we may then regard the number of chromosomes 
in the gameto-nuclei as four, in the nuclei of the germinating 
oospores — the gametophytic mycelium that is to say — 
as eight. 
It was not to be expected that the finer details could be 
seen so well in this case as in the gametangia, for the fixing 
fluid has to penetrate the thicker wall of the oogonium and 
the thick resistent wall of the oospores as well. 
Criticisms and Replies to Criticisms. 
Having made myself thoroughly acquainted with a species 
of Achlya , and solved the problems which presented them- 
selves at the commencement of the work, I found myself 
in a position to examine critically the results obtained by 
Humphrey and Hartog. 
On the evidence of Humphrey’s (’ 94 ) own figures I had 
concluded, as a result of my work on Saprolegnia , that fertili- 
zation took place in Achlya americana . Humphrey’s view 
that the uninucleate oospores were derived from the binucleate 
ones by fusion of the two nuclei was obviously correct ; but 
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