INTRODUCTION. 



proved by the case described by me in Journ. Linn. Soc., 

 vol. xxix., p. 541. In that instance a plasmodium of B. utri- 

 cularis growing on Auricularia 'mesenterica partly spread in a 

 network of veins over two large coverslips ; the films were killed 

 with Flemuiing's fluid, stained with safranin, and mounted in 

 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 

 Auricularia 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 f ollow- 

 observations confirm the 



ng 



conclusion arrived at from 

 many previous experiments, 

 that it is not the only way 

 by which the nuclei 



FIG. 6. BADHAMIA UTRICCLARIS Berk. 



Group of nuclei from actively feeding 

 increase Pl asm dium that covered two pilei of 

 Auricularia in fourteen hours, showing the 



in number. A further growth irregular size of the nuclei and large nucleoli. 



of the plasmodium 



VP 

 le 



ferred to as increasing sixfold in 



Stained in picro-carniine and mounted 

 i Canada balsam. 

 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, part 

 2iassu, 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 /z, 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. 



