530 MR. A. LISTER OX THE DIVISION OP 



process the multiplication of these nuclei came about. During 

 this time I have made many stainings of the plasmodium of a 

 large number of species, and though I have often seen appear- 

 ances which implied that simple division took place, I was never 

 able to detect the smallest indication of karyokinesis. 



From the cultivation of plasmodia it was obvious that there 

 was a continual increase in the number of the nuclei. Jiadhamia 

 utricular is affords especial facilities for such cultivations, as it 

 grows rapidly when supplied with such fungi as Stereum hirsutum 

 and Poly poms versicolor. 



In January 1887, 1 gathered the plasmodium of Badhamia from 

 a stump in my garden, and from that time to the present I have 

 had an almost continuous series of cultivations from that one 

 source. I have sometimes had as manv as 17 colonies growing at 

 once ; some of these would change to sporangia and some I 

 allowed to drv into sclerotium, which at any time I could revive 

 to replace those that had produced their spores # . 



Stainings of the plasmodium made at any time of the year, 

 and either immediately previous to the change to sporangia or 

 weeks before, always showed the nuclei of the same character : they 

 are about 3 ju in diameter, varying from 2 # 5 p to 5 p (PL XXXV. 

 fig. 1) ; they contain usually a single nucleolus but sometimes two 

 or three of smaller dimensions. 



Considering that the plasmodium with which our stainings 

 were made was suddenly killed when in full vitality and preserved 

 so perfectly that the minute vacuoles in the thinnest parts of the 

 film were distinctly defined, it is perhaps remarkable that we do 

 not more frequently meet with unmistakable instances showing 

 the nuclei in the actual process of division, but such is the fact. 

 Although we know that rapid multiplication of nuclei must go on 

 in quickly-growing plasmodium, we may search a mounting for a 

 long time without meeting with the dividing stage ; at the same 

 time it is met with frequently enough, I think, to justify the 

 conclusion that the nuclei multiply by simple division. Fig. 2, 

 a, b (PI. XXXV.), represent some of the forms in which such 

 division appears to be going on. In almost every field of the 



* The encysting of the plasmodium when it passes into the condition of 

 sclerotium appears to be analogous to the formation of microcysts in the 



swarm-cells : a number of nuclei with the accompanying plasma are inclosed 

 by a cyst-wall, which i9 either dissolved or remains persistent according to the 

 species, when the sclerotium is revived; but there is nothing to lead us to 

 suppose that nuclear division is involved in the process. 



