176 j. j. lister. 



Description of Plates. 



List of Reference Letters. 



b. Brown bodies. 



c. Spiral canal in the umbilical region of the shell. 

 /. Foreign particles. 



M. Megalosphere. 



m. Microsphere. 



N. Nucleus. 



s. Bodies in the protoplasm, staining red with picro-carmine, and 

 here regarded as nutritive in nature. 



St. Stained strands. 



V. Vacuole. 



Figs. 1 to 33, with the exception of 4, a and 6, relate to Polystomella 

 crispa (Linn.). 



Fig. 1. X 230. Part of a megalospheric specimen in which the nucleus 

 has been involved in a movement of the protoplasm, probably the effect of 

 the reagent. N. The main mass of the nucleus. ^V. Portions of the 

 nucleus carried on by a movement of the protoplasm. Sublimate and 

 picro-carmine. 



Fig. 2. X 250. Example of a megalospheric individual in which the 

 protoplasm contains numbers of spherical bodies (s), probably nutritive, 

 which take a red stain in picro-carmine. 



Fig. 3. X 523. End of one of the chambers of a similar specimen. 



Fig. 4a. X 690. Balantidium entozoon (Ehr.). Specimen containing 

 numbers of darkly staining spherical bodies, probably nutritive. 



Fig. 46. X 1460. One of the spherical bodies from another specimen 

 of Balantidium entozoon. Osmic vapour, picro-carmine. 



Fig. 5. X 1047. End of a chamber of a specimen containing brown 

 bodies (6). 



Microspheric form. 



Fig. 6a. X 170. Complete specimen, with forty -two* chambers. As 

 the series of chambers is followed towards the centre, the nuclei lose their 

 rounded shape, and strands of nuclear substance are seen scattered through 

 the protoplasm. 



* This is the number of chambers of whose presence there are indications in 

 the decalcified specimen. It frequently occurs that in the live state one or more 

 of the terminal chambers contain little or no protoplasm, and hence might not 

 be represented after decalcification. The same remark applies to the other de- 

 scriptions in which the number of chambers is given. 



