RECENT RESEARCHES ON OOGENESIS. 595 
Analogous Processes in Plants.—In his last memoir 
(1884) Strasburger (4) notes numerous instances where por- 
tions of the reproductive cell are excluded by extrusion or 
otherwise from the differentiated result. Thus, in the female 
cellsof Vaucheria and @dogonium there is an expulsion of 
the colourless protoplasm which collects at the anterior pole. 
From the ova of Archegoniatz, shortly before maturation, 
a “ Bauchkanalzelle” is separated off by ordinary division, 
and a similar cell is formed in Conifere, and irresistibly 
reminds one, he says, of the polar cell of the animal ovum. 
In the differentiation of the male cell analogous processes may 
occur, unused material is extruded along with the spermato- 
zoids from the antheridia of Fucus; a similar remnant is ob- 
servable in Vaucheria, while the spermatozoids of Archego- 
niatz are formed from the nuclear substance round a central 
vesicle, which retains the unused portions of the spermatocytes. 
In Salvinia a portion of the protoplasm is at an early stage 
excluded from the formation of the four spermatocytes. The 
“secreted body” (‘‘ secret-K6rper”) which Strasburger found in 
the mother-pollen cell before division, has been collated by 
different authors (e.g. Nussbaum) with the excentric pro- 
blematic body (Nebenkorper), which has been described in the 
spermatogonia of Astacus, Helix, &c., and which seems to 
disappear as division sets in. Strasburger’s recent researches 
on the ontogeny of pollen grains suggest also similar compari- 
sons with processes in the differentiation of animal sex-cells. 
In Gymnosperms the prime pollen-cell or “ progame”’ divides 
into a smaller vegetative and a larger reproductive portion; the 
latter may again divide once or twice, and the result is a gene- 
rative cell, with, perhaps, three rapidly dwindling vegetative 
cells. Since these vegetative cells are successively divided off 
from the reproductive they are for this and other reasons not 
comparable with a prothallium. In Angiosperms the process 
is essentially similar. In all cases the vegetative nuclei, sepa- 
rated off from the reproductive, disappear without playing any 
role and without dividing. 
In regard to the extrusions formerly cited, it must be allowed 
