552 Trow . — On Fertilization in the Saprolegnieae . 
It is clear that the work on Achlya polyandry Hildebrand, suffices to enable 
us to add another species to the list of the Saprolegnieae in which func- 
tional sex has now been established. 
Observations on Achlya De Baryana , Humphrey. 
Figs. 14 to 34 serve to illustrate all the fundamental features of the 
cytology of this species. These may be compared with the corresponding 
figures published by me in ’95 and ’99, as well as with Figs. 1 to 13 . 
Novel or controversial points will alone be discussed in this paper. 
The structure of the nucleus in the Saprolegnieae and the first mitosis 
in the oogonium. The resting nucleus of the Saprolegnieae has, in common 
with many other fungal nuclei, been frequently figured as consisting of 
a central chromatic body separated from the investing nuclear membrane 
by an achromatic perfectly hyaline substance. Davis (’03) occasionally 
represents the nucleus as of this type, as e. g. in Figs. 31 to 35 of his recent 
paper. However, Davis’s description, with which most of his figures agree, 
gives a correct account of the actual appearances. He says, ‘There is 
a nuclear membrane enclosing a well-differentiated nucleolus, prominent by 
its size and staining qualities. Much less conspicuous, but readily demon- 
strated in well-fixed material, is a loose linin network which contains the 
chromatic material.’ The observations summed up in this statement agree 
with my own recent ones ; they do not differ, indeed, in point of fact from 
those I published in ’99. Still, I must object to the view that the 
central body has been proved to be a nucleolus. This is not so much 
a question of the relative value of preparations, concerning which every 
botanist may be allowed to have his own opinions, but rather of the inter- 
pretation of observations. If this conspicuous structure is a nucleolus, it is 
a giant of its kind, and such nucleoli in the higher plants would excite 
considerable interest. I have looked in vain for figures of such. My 
present conception of this problematic body, which I provisionally regarded 
as a ‘ chromosome 5 in ’95, may be best realized if one imagines the 
nucleolar matter in the nucleus of a lily to increase in amount to such an 
extent as to half fill the nuclear cavity, and in doing so, to enclose, not 
displace, a large portion of the pre-existing linin network and the 
associated chromatin. This view, first promulgated in ’99, I am not yet 
prepared to discard. It is based mainly on observations made on the 
central body during the prophases of karyokinesis. It is in accordance 
both with Davis’s figures and the descriptions of his observations, but is in 
conflict with his interpretation of these ; whether in the light of the recent 
researches of Wisselingh (’00) this view finds corroboration or not, seems to 
me of little importance. According to Wisselingh, the so-called nucleoli of 
Spirogyra give rise during karyokinesis to distinct chromosomes. The 
nuclei of the Saprolegnieae are not very suitable objects for the elucidation 
