ABSTRACT AND REVIEW. 99 



swimming (compare Lankester's figure [9]). lu this condition 

 they never divide, and are always circular or elliptical. The 

 dark central mass which contains the nuclei and chromatophores 

 is surrounded by a margin of clear protoplasm, from which 

 emanates a halo of hyaline pseudopodia, which continually 

 shorten and lengthen again, or may be altogether withdrawn 

 and then again protruded. These pseudopodia are similar to, 

 although much larger than, those of the creeping amoebae, 

 which latter are only developed on the forwardly directed end 

 (Fig. C). Along them move numerous round or spindle-shaped 

 physodes, carried hither and thither by the streaming of the 

 protoplasm. The emergence of the amoebae from their cysts, 

 and their subsequent division, only take place during the 

 summer months, and then only during the warm hours of the 

 day, and in the presence of light of sufficient intensity. 



In the amoebae the olive-green or red oil bodies are never 

 seen, nor the crystals of calcium oxalate ; but both are fre- 

 quently found in deserted cysts, being sometimes egested at 

 the moment of emergence. 



b. The Cysts. — The form of the cyst, when on the surface 

 of leaves, etc., is generally spherical or ovoid, occasionally 

 elongated or irregularly lobed, the last when large Algae have 

 been ingested. In the case of those cysts, however, which are 

 inside the cells of the plants on which they live, the form is 

 adapted to that of the cell ; but if this is too small for the 

 enclosed cyst, the latter may protrude (cf. Geddes, fig. 1) as a 

 hernia-like swelling into which a portion, or in some cases the 

 whole, of the protoplasmic contents migrate. A new spherical 

 cyst forms round the protruded protoplasm, while the old cyst 

 splits, thus allowing the newly formed one to escape without 

 becoming amoeboid. 



Again, it often happens that the protoplasmic contents 

 divide into two or more parts, each forming a proper cell-wall 

 of its own. The large many-layered cyst described by 

 Archer, enclosing several small cysts, is probably a sort of 

 formation of resting spores. The repeated formation of 

 a new membrane round, and the subsequent division of the 



