128 Wager . — Observations on the Structure 
says : — ‘ The objects under consideration, except in the Sapro- 
legnieae, are of such minute size, that the satisfactory discrimi- 
nation of true nuclei from other small bodies contained in the 
protoplasm, and like them perhaps rendered more distinct by 
colouring reagents, is extremely difficult, and can only be ob- 
tained after renewed investigation.’ 
There is, as is well known, no decisive test for nuclei except 
the morphological one of structure. Zacharias 1 and others 
have, it is true, done much to show that the presence of a 
nucleus or nuclear substance may be determined by chemical 
means ; but their results, although they are extremely valuable, 
are not sufficiently satisfactory or definite to be of much use 
in determining whether the minute deeply staining bodies 
present in the protoplasm of many of the lower plants can be 
looked upon as nuclei or not. It is therefore necessary, in 
order to decide whether in any given case the numerous 
small bodies in the protoplasm should be looked upon as 
nuclei— in the same sense in which we speak of them in the 
higher plants and animals— to show that they have some per- 
fectly definite structure which distinguishes them from the 
other bodies in the protoplasm. This has been shown to be 
the case in certain of the fungi. In the Saprolegnieae, for 
example, the resting nuclei have a structure which is distinctly 
comparable with the structure of the nuclei in the higher 
plants, and in some other fungi a perfectly characteristic 
structure has also been found to exist. 
Perhaps the most important factor in the determination of 
this question lies in the division of the nucleus ; where this is 
indirect or karyokinetic we have the most satisfactory proof 
of the nuclear nature of the body in question. It is not 
necessary that the changes which take place during this 
karyokinesis should be so complicated or so numerous as 
those which take place in the higher plants. It is sufficient 
if we are able to recognise that the division is one which con- 
forms to some simple generalisation in which the changes 
1 Bot. Zeitung, xlv, 1887. 
