THE UNICELLULAR ORGANISMS. 75 



XXI. Oue of the same, after two or three days' immersiou in water under the 

 microscope. 



XXII. Later phases in the motile stage assumed by the above. 



The black spot indicates the red colouring-matter present, and the extreme left-hand 

 figure is that of an individual destitute of cellulose investment. (Bergh, Morph. Jahrb., 

 vol. vii., 1881, has discovered a cellulose investment for certain chlorophyll-bearing 

 Protozoa.) 



The Yeast Plant. 



FIG. XXIII. Cells of ordinary brewer's yeast, 

 i.-iv. Stages in division of the same cell. D. 4. 

 i. a Fig i. as seen under Gundlach's ^th immersion. 

 v. A branching colony, still retaining their original connections. 



Schmitz, Stzb. Bonn, August, 1878, has described in the yeast-cell, and in certain other 

 low organisms, Mucor among their number, what he considers to be a nucleus. 



FIG. XXIV. The endogonidia (ascospore) phase of reproduction, as seen in a sample of 

 yeast sown on a slab of gypsum. F. 3. 

 Bee Huxley (111) and Eees (120). 



FIG. XXV. Further development of the endogonidia, after transfer to Pasteur's 

 solution. F. 3. 



The Bacteroid. 

 FIG. XXVI. Micrococcus. 



FIG. XXVII. Bacterium. 



FIG. XXVIII. Bacillus. 



The central filament of this series segmented up, as drawn, within ten minutes of its 

 detection. 



FIG. XXIX. Spirillum. 



i., ii. represent the so-called Vibrio. It is probably but a stage of Spirillum. 



FIGS. XXX. and XXXI. Two giant Spirilla. 



FIG. XXXII. A drop of the surface scum, showing a Spirillum aggregate in the 

 resting state. 



