Trow. — On Fertilization in the Saprolegnieae. 555 
some nor astrosphere. Cases such as g and h require attention. In k the 
association of the centrosome and astrosphere with its nucleus is clear. 
The centrosome is in close contact with the nuclear membrane. From 
a study of^ an observer might conclude that the centrosome was attracting 
to it the adjacent nucleus. Considerations such as these, combined perhaps 
with preconceived ideas as to the distribution and physiological significance 
of ‘coenocentra,’ may have led Davis astray when working at this very 
complex problem. 
Against the adequacy of the proof furnished here of a second mitosis 
taking place, it may be urged that the peculiar appearance of elongated 
spindles may be explained more easily and naturally on the assumption 
that we have before 11s a case of the division of the centrosome and the 
formation of an extra-nuclear spindle, the nucleus itself remaining undivided 
or its division being overlooked. Such a contention must not be lightly 
dismissed. Certain observations, relatively few in number serve, however, 
to dispose of it effectually. Nuclei in the nuclear-plate stage are occa- 
sionally seen as at k and / — the latter, it is well to note, in an antheridium. 
These nuclei are provided with a nuclear membrane, and are certainly 
undergoing a second mitosis. A comparison of the earlier stage in the 
development of the oogonium represented in Fig. 17, where all the nuclei 
have completed the first division, and of the still earlier stages represented 
in Figs. 15 and 16, where all the nuclei are undergoing division, with 
this one, must convince any unprejudiced observer that there can be no 
question here of the inadmissibility of the explanation that these early 
metaphases may belong to a deferred first mitosis. The dissimilar elongated 
nuclei seen in late metaphases and anaphases are, no doubt, derived from 
the earlier metaphases by the loss of the nuclear membrane and the elonga- 
tion of the spindle. Harper (’ 99 ) has figured a similar elongation of the 
spindle in the nuclear divisions in the ascus of Lachnea. The apparent 
absence of the astrosphere in early metaphase, when at best it must be very 
feebly developed, is of little importance. It is only in very late anaphases 
that it makes itself really conspicuous. 
Degeneration of the supernumerary nuclei. There are one or two points 
which must be clearly borne in mind when endeavouring to clear up the 
difficulties associated with the actual observation of the degeneration of the 
nuclei. A functional nucleus is only definitely recognizable by its structure, 
and in general that structure is only demonstrable in well-stained pre- 
parations. Degeneration is associated with loss of structure. Degenerate 
nuclei must therefore soon become unrecognizable. The degeneration and 
digestion of the nuclei is very rapid in Achlya , indeed much more so than 
in Pythium. Badly-stained nuclei associated in the same section with 
well-stained ones must be regarded as degenerate. We have to try and 
arrange these in a consecutive series to form some idea of the process of 
Qq 
