146 J. J. LISTER. 



numbers of actively moving spherical spores were set free in the 

 water, while numbers of bodies, similar in all respects except 

 their activity, remained among the broken fragments of the 

 shell. On staining these with acid gentian violet indications of 

 two flagella were made out, but the spores were too darkly 

 stained for the nuclei to be detected. The spores were approxi- 

 mately of uniform size (4 to 6 /u. in diameter), and, except for 

 certain dark yellow masses, and some brown granules, con- 

 stituted the whole of the contents of the shell. 



It appears most probable that these actively moving spores 

 are identical with the spherical masses seen in the preserved 

 specimen last described. The difference in size may be 

 accounted for by the difference in the modes of preparation. 



It will be noticed that while the masses in which the 

 dividing nuclei lie have a diameter of 3 to 4 /i, the spores, 

 which it appears are produced by the division of these masses, 

 have an almost equal diameter (3 to 3'5 fi). It is probable 

 that the spores owe their large diameter to the more vacuolated 

 condition of their protoplasm. 



On another occasion, the bodies which are represented in 

 Fig. 33 a and h emerged from a specimen of Polystomella. At 

 first I regarded these as anisospores produced by Polystomella, 

 but I am now inclined to the view that they were produced by 

 some other organism which had entered the shell. 



The evidence afforded by the investigation of Polystomella 

 may now be reviewed. 



The Microspheric form occurs in various phases of develop- 

 ment, both young and old specimens having been found (figs. 6 

 and 7). Numbers of small nuclei are present, scattered through 

 the protoplasm, but not extending into the terminal chambers. 

 Those in the inner chambers are smaller than those situated 

 further on. The nuclei contain nucleoli of different sizes lying 

 in an apparently homogeneous inter-nucleolar substance. The 

 nuclei increase in number by simple division, and it appears 



