INTRODUCTION, 
9 
proved by the case described by me in Journ. Linn. Soc, 
vol. xxix., p. 541. In that instance a plasmodium of B. utri- 
cuiaris growing on Auricularia mesenterica partly spread in a 
network of veins over two large coverslips ; the films were killed 
with Flemming's fluid, stained with safranin, and mounted m 
Canada balsam. In these two preparations the nuclei are seen 
to be dividing by karyokinesis ; the stages represented are the 
nuclear spindle, and where the nuclear plate has divided and the 
two halves are connected by achromatic fibres. Part of the same 
Plasmodium spread over another coverslip, and was killed and 
stained with the others. The nuclei in this preparation have 
the appearance most commonly met with, containing a central 
nucleolus, and without any indication of karyokinetic division. 
The main body of the plasmodium continued to creep over the 
AiLvicularia for several days after these observations had been 
made. 
This experiment affords clear 
evidence that under certain 
conditions the nuclei of the 
actively streaming plasmodium 
divide by karyokinesis, but 
what these conditions are re- 
mains at present unexplained. 
The process no doubt is a 
rapid one, occupying about 
half an hour; but the follow- 
ing observations confirm the 
conclusion arrived at from 
many previous experiments, 
that it is not the only way Group of nuclei from actively feeding 
by which the nuclei increase Plasmodium that covered two pilei of 
,J API 1 Aunmlana in fourteen hours, showing the 
m number. A further growth irregular size of the nuclei and large nucleoli. 
of the Plasmodium already re- i^^cSl Cisar°"""""' 
ferred to as increasing sixfold in Magnified 1200 times, 
twenty hours, spread over two 
pilei of Auricularia in the course of fourteen hours ; during this 
period a portion of the plasmodium was taken every quarter of 
an hour, and smeared on a thin coverslip and stained. Each of 
the fifty- five mountings shows the nuclei in the usual vast 
abundance, implying that their numbers had increased, pari 
passu, with the growth of the plasmodium, and in none of them 
is there any appearance of karyokinetic division. From previous 
observations of the length of time occupied by the karyokinetic 
process we are satisfied that it could not have escaped detection if 
it had occurred during those fourteen hours. The multiplication 
of nuclei which we are bound to assume had taken place must 
therefore have been produced by some other means. They 
vary in size from 2 '5 to 5 /x, and the great majority contain 
a single sharply defined and deeply stained nucleolus, which is 
seen to be connected with the nuclear-wall by delicate threads. 
Fig. 6.— Badhamia utbiculakis Berk. 
