No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 
Linens gesserensis. —Cells of the first type : one or two small 
nucleoli. Cells of the second type : one nucleolus. Cells of 
the third type : a single nucleolus, or two of unequal size. 
Cerebratnlus lacteus. — Cells of the first type : as in the 
preceding species. Cells of the second type : one or two 
nucleoli. Cells of the third type : one or two nucleoli, which 
in one case stained differently. Cells of the fourth type : 
usually one peripheral nucleolus; rarely are two present, and 
then they are unequal in dimensions. 
In all these cells the nucleolus is comparatively small, homo¬ 
geneous, and no evidences of nucleolar division were seen. 
IV. GENERAL COMPARISONS AND CONCLUSIONS. 
Here I shall summarize merely the results of my observations 
on the nucleolus, and compare them with the conclusions of 
other investigators. Numerous other morphological points 
have been brought up, however, in the preceding pages, such 
as yolk development, differentiation of ova, nuclear divisions, 
distribution of the chromatin elements in the germinal vesicle 
at different stages in the growth period, changes in the struc¬ 
ture of cytoplasm, etc. 
i. Chemistry of the Nucleolus. 
I have made no special chemical study of these structures, 
except what may be learned from their reactions to stains. In 
the gregarines no substance could be demonstrated which chemi¬ 
cally corresponds to the chromatin of the metazoan cell ; 1 but the 
following table represents the mode of staining of true nucleoli 
in the somatic and germ cells of the Metazoa: 
Stain. 
Nucleolus. 
Chromatin. 
Del. or Ehrl. haematoxylin, eosin 
. red 
. blue. 
Ehrlich-Biondi stain . 
. maroon or red 
. green. 
Acid carmine, nigrosine 
. blue or greenish 
. red. 
Del. haematoxylin, cochineal 
. pink or red 
. blue. 
Safranin, gentian violet, orange . 
. yellow 
. blue. 
Schwarz (’ 87 ) distinguishes in 
plant cells pyrenin, the sub- 
stance of the true nucleoli, from the other nuclear substances 
1 That is, not to chromatin in the form of pure nucleic acid. 
