368 ALFRED GIBBS BOURNE. 



considerable. I have found it to be about 075 mm. a 

 minute. Eugelmann^ states that a velocity of 0*5 mm. a 

 minute is sometimes attained by an Amoeba, and may be con- 

 sidered as exceptionally rapid. I have made my observations 

 at the ordinary temperature of the room ; but this is about 

 30° C. at this time of year, and is thus not far below the 

 optimum temperature for protoplasmic movement. 



Nuclei. 



The number of nuclei present is enormous. I have en- 

 deavoured to estimate the number on stained preparations. 

 I have made these preparations in various ways ; one of the 

 most satisfactory is to fix and harden on the slide with 

 chromic acid (2 per cent, solution), followed by water and 

 alcohol of increasing strengths; stain with picro-carmiue, 

 wash, and again treat with alcohol of increasing strengths ; 

 dehydrate, clarify, and mount in Canada balsam. 



I put down the number of nuclei present in a large indi- 

 vidual at 10,000. 



They vary a little in size, but average, when living, about 

 0'03 mm. in diameter. 



It has struck me that there may be some connection 

 between the bulk of nuclear matter and the bulk of proto- 

 plasm connected with it. 



I calculate that in P. viridis all the nuclei taken together 

 occupy -^ of the total bulk of the organism. 1 have not 

 many data at haad for comparison with this calculation, but 

 in a mammalian ovarian ovum the nucleus occupies about 

 ^ of the bulk of the ovum. So that 10,000 nuclei in P. 

 viridis give relatively about the same bulk of nuclear mat- 

 ter as is found in a mammalian ovum. The nuclei closely 

 resemble the nuclei of other species of Pelomyxa. 



In a fresh condition they are spherical, and consist of a 

 nuclear membrane containing a perfectly clear and trans- 

 parent fluid nuclear substance, in which are seen from nine to 

 twelve highly refracting spherical nucleoli (fig. 7). 



' L. c, p. 379. 



