NUCLEI IN THE MTCETOZOA. 541 



sharp as in the mountings in balsam stained with picrocarmine, 

 it was abundantly sufficient to indicate the period at which it 



was desirable to make frequent preparations *. 



In reviewing the observations recorded in this paper we find : — 



1. Karyokinesis takes place in the nucleus at the time when 

 the swarm-cell divides. From former observations we know 

 that when the swarm-cells unite to form the plasmodium, their 

 nuclei remain distinct and do not coalesce. 



2. The examination of over a hundred stainings of streaming 

 Plasmodium in which we know that the nuclei have multiplied 

 in vast numbers, and in which no indication of karyokinesis 

 occurs, leads to the conclusion that they increase by simple 

 division. Although from the nature of the case such division 

 must be difficult to detect, we frequently meet with appearances 

 which support this conclusion from actual observation. 



3. Within one hour before the formation of spores in the 



sporangium, in other words, when division of the protoplasm into 



true cells takes place, we have again the phenomenon of karyo- 

 kinesis. 



Or, leaving aside the question of the sclerotium, we may further 

 generalize thus : — 



Whenever cell-formation occurs in the life-history of the 

 31ycetozoa, the nuclei divide by karyokinesis. 



Additional Note. — Since writing this paper, convincing proof 

 has been obtained that, under certain conditions, the nuclei in the 

 streaming plasmodium divide by karyokinesis. 



Mr. J. J. Lister, of Cambridge, has just repeated experi- 

 ments with the plasmodium of BadJtamia utricularis. A portion 

 of sclerotium of this species was revived, and the plasmodium 

 spread itself in large fans over a thin cover-glass. Four of these 

 films connected by veins of plasmodium were taken at the same 

 time and killed with Flemming's fluid and stained. Two of the 



* I have lately succeeded in making permanent mountings of the swarm- 

 cells of Amaurochate and Reticularia by the following method :— A drop 

 of water containing the swarm-cells is mixed with a small quantity of Flemming's 

 fluid on a square cover-glass ; it is allowed to evaporate almost to dryness, suffi- 

 ciently to permit the objects to adhere to the glass, which is then floated on a 

 watery solution of Erlich's hematoxylin and stained for twelve hours, washed 

 for two minutes, passed through alcohol from 30 per cent, to absolute, then 

 through oil of cloves, and mounted in balsam. 



The karyokinetic figures in these preparations show the spindle-fibres more 

 clearly than in the best of the fleeting stainings with acetic gentian-violet. 



