358 ALFRED GIBBS BOURNE. 



Habitat and General Description. 



I have only found P. viridis in one tank, and this a tank 

 which has not been known to dry up for many years. 



When the mud from this tank is placed in a dish with a 

 little water and allowed to stand, several individuals of P. 

 viridis may generally be found close to the surface of the 

 mud ; if these are removed and the mud stirred up and again 

 allowed to stand, it is not usual to find many other specimens. 

 So that I believe that this Rhizopod lives close to the surface of 

 the mud. I have never seen it crawling on the sides of the 

 dish or on any other object; nor have I ever seen it much 

 spread out while in the mud, but when mounted on a slide with a 

 cover-glass it readily spreads itself out and becomes very flat, 

 and soon commences to exhibit active amoeboid movements. 

 Fig. 1 represents a mounted specimen, partially spread out 

 and magnified about four diameters. It is difficult to convey 

 any idea of the size to which such an organism may attain, as 

 so much depends upon the extent to which it is spread out. I 

 have seen specimens so much spread out that they would 

 average as much as ^ inch in diameter. The specimens are of 

 very varying sizes, but I have never found very small speci- 

 mens ; I have never, in fact, been able to find a specimen by the 

 aid of the microscope which I had not previously picked out 

 with the naked eye, although I have searched many slides of 

 the mud for this purpose. It may be that small individuals 

 are to be found at some other time of year, or it may be that 

 I have not, in spite of my search, happened to alight upon a 

 small specimen. 



When viewed by reflected light individuals vary a good 

 deal in colour, from the rich transparent green of a gelatinous 

 lichen to that of a faded leaf. I presume that the chlorophyll 

 undergoes some degeneration. I have never found any 

 approach to the red colour found in Euglena or Haemato- 

 coccus. There is often a whitish, more opaque-looking spot, 

 such as has been shown in the middle of fig. I. This is caused 

 by au aggregation of sand particles, and it is often more clearly 

 defined than in my figure. When seen by transmitted light 



