156 
R. T. Young 
of which a developing membran'e is very faintly suggested. Tlie fourtli 
mass contains a distinct »nucleolus« surrounded by a small light area 
and several very minute granules, while around tlie whole a developing 
membrane is very faintly outlined (Fig. 16). The fifth mass is small, 
homogeneous and darkly stained. It is donbtless nuclear in character 
but lacks membrane or definite outline. These, and similar nuclei in tlie 
same material, suggest not only a de novo formation of nuclei, but also 
a physiological modifieation of cells, whereby some of these become either 
impregnated tlrruout with nuclear material or eonverted bodily into 
such material 1 ). 
Among 1500 nuclei examined 2 ) no mitoses were found 3 ). Some cases 
were seen suggesting a possible amitosis of pre-existent nuclei. As to 
the relative parts played by tlie amitotic and de novo methods of nuclear 
increase in this vorm, I cannot sav. 
Tetrarhynchus crenacolle. 
(Fig. 17.) 
While this material presents little evidence of de novo formation 
it shows well the difference in staining reaction between different cells 
which I liave mentioned so frequently elsewhere. Tlie cell bodies are 
irregulär in shape tho usually spherical or ovoid, and vary in size as well 
as staining density. In some tliere is but a single small granule densely 
stained, while in others the entire cell body is so. Auelei are therefore 
in no way distinguishable from the cytoplasm, save in staining density. 
The distribution of staining matter tliru the cell is usually irregulär, it 
being collected in masses of varying shape and size. 
No evidence of mitosis 3 ) was found liere in an examination of 
1000 nuclei 2 ). 
Coenurus serialis. 
(Fig. 18.) 
In the sub-cuticula I find a majority of the cells lacking anv de- 
finite nuclear structure, while in others nuclei are more or less definitely 
outlined. ln tliose cells which lack definite nuclei some stain dark blue 
x ) In view of the results of micro-ckemical tests on Taenia crassicollis the former 
hypothesis is the more probable. See p. 148 — 151. 
2 ) See footnote 1), p. 145. 
3 ) See footnote 3), p. 155. 
