RECENT RESKARCHES ON OOGENESIS. 599 
terms of physiology. Their physiological import, if discovered, 
might shed light on the meaning of alleged extrusions among 
Protozoa and lower plants, while it is in a study of these that 
the morphological import of polar cells is perhaps most hope- 
fully to be sought. The general theory suggested by Fol, 
Giard, Mark, Whitman, Flemming, and others, is that polar 
vesicle formation represents phylogenetically the survival of an 
asexual or parthenogenetic division, diminishing, according to 
Mark, for the good of the ovum. Minot suggestively com- 
pared the process to the nuclear extrusion alleged to exist 
in Infusoria. 
Biitschli (6) has lately (1884) made a more detailed attempt 
to determine the morphological import of these cells. Refer- 
ring to the colonies of sexual cells formed by multiplication in 
such organisms as Eudorina and Pandorina and Volvox, he 
suggests that polar cell-formation is an all but obliterated 
survival of the early colony formation. 
Physiological Import.—Speculations as to the physio- 
logical meaning of the polar cells are abundant enough. Some 
regard them as effecting a desirable lessening of the nuclear 
mass, either to prevent parthenogenesis, or to decrease the dis- 
proportion between female and male nucleus. Minot (7) 
regards them as definitely male elements, retained in parthe- 
nogenesis, necessarily excluded to secure sexual differentiation, 
and compares them with the sperm blastophor, while it has 
been also maintained that in their extrusion the more passive 
portion of the germinal vesicle is expelled. Brass (‘ Zool. 
Anz.,’ 1882) compares them to vacuole contents of amebz, 
and regards them as the excretory products of an actively 
functioning cell. Since such speculations are for the most 
part still too indefinite and in some cases too teleological, it 
will be sufficient to note three of the most recent, those of 
Sabatier (1884), Strasburger (1884), and Weismann (1885). 
As the result of his comparative study of spermato- and 
oo-genesis, Sabatier (3) was led to observe (1) that the male 
elements resulted from differentiation in the peripheral or 
protoplasmic portion of the reproductive cell, while the nuclear 
