spirostomum ambiguum 433 



Books of General Eeference. 



Delage, Y., and Herouard, E. (1896). — ' Traite de Zoologie Concrete. 



I. La cellule et les Protozoaires ', Schleicher Freres, Paris. 

 Doflein, F. (1916). — ' Lehrbuch der Protozoenkunde ', Gustav Fischer, 



Jena. 

 Kent, W. Saville (1880). — 'Manual of the Infusoria', David Bogue, 



London. 

 Minchin, E. A. (1912). — ' An introduction to the study of the Protozoa ', 



Edward Arnold, London. 



9. EXPLANATION OF PLATES 22 AND 23. 



Pig. 1.^ — Part of the meganucleus of an ordinary individual. L., a lobe 

 of the meganucleus. C, a commissure. M.N., a micronucleus surrounded 

 by a halo, m., a non-vacuolated macrosome. vac, a macrosome con- 

 taining a small vacuole, x 1200. 



Fig. 2. — Part of the meganucleus of a normal individual. MV ., large 

 macrosome. vac, vacuole inside the macrosome. x 1200. 



Fig. 3. — The terminal lobe of a similar meganucleus. x 1200. 



Fig. 4. — Part of the meganucleus of an ordinary individual undergoing 

 fission, with the meganucleus contracted towards the anterior end of the 

 body. X., the anterior end of the meganucleus. 31. N., swollen micro- 

 nuclei surrounded by halos. x 1200. 



Fig. 5. — Isolated lobes of the fragmented meganucleus of a conjugant. 

 vac, vacuoles inside the lobes. !>., pale-staining spheres appearing inside 

 some of these vacuoles, x 1200. 



Fig. 6. — The nuclear apparatus of a young exconjugant. L., the darkly 

 staining fragments of the old meganucleus. A., the newly forming mega- 

 nuclei, as yet very pale. The presence of as many as five newly forming 

 meganuclei in one exconjugant is unusual, x 1200. 



Fig. 7. — A preparation of a pair of conjugants showing tho mega- 

 nucleus in a fragmented condition, x 120. 



Fig. 8. — One single large sphere of the newly forming meganucleus 

 present in an exconjugant. MV., macrosome-like bodies, x 1200. 



Fig. 9. — Pointed spindle T)f a micronucleus in a conjugant. X 1200. 



Fig. 10. — Globular spindle of a micronucleus in a conjugant. x 1200. 



Fig. 11. — Swollen micronucleus with unevenly distributed chromatin 

 at one side and spindle-threads forming at the other, x 1200. 



Fig. 12. — Part of a conjugant. 31. N., micronuclei very much swollen. 

 The distribution of chromatin in the swollen micronuclei is very uneven. 

 3I.X., a micronucleus which is less swollen. L., isolated lobes of the old 

 meganucleus. x 1200. 



