RECENT RESEARCHES ON OOGENESIS. 605 
wards, but remains in the bosom of the vitellus. Sabatier 
(‘ Comptes rendus,’ 1883) has also observed a yolk nucleus in the 
arachnid ovum, originating near or even in contact with the 
germinal vesicle, but not from it, a male centrifugal element 
breaking up at the periphery. 
A recent important contribution is due to Will, whose 
researches relate for the most part to insect ova. He describes 
the morula-like division of the primitive nucleus or ooblast, 
the appearance in some cases of buds covering the whole surface 
of the germinal vesicle, and tie migration of the daughter- 
nuclei to the periphery, leaving, however, a residue which forms 
the final germinal vesicle, often at first with but little chromatin 
left. The migrating daughter-nuclei seem sometimes simply 
to form part of the yolk, in other cases they result first in 
distinct epithelial cells, which afterwards share in the yolk 
formation. He has also described how the nuclei of the 
“nutritive cells,’ which result from the early division of a 
generative cell, may either dissolve away and help to form 
nutriment outside the ovum, or may wander out of their cells, 
and, reaching the ovum, also form epithelial cells, and thus also 
share in the formation of yolk. 
Many of these observations must await further confirmation, 
but the fact that Fol, Nussbaum, Sabatier, Roule, Balbiani, 
Will, and others agree in deriving the follicular cells from the 
ovum itself, and all of those cited, with the exception of Saba- 
tier, from the germinal vesicle, warrants some confidence in 
results so suggestive, both in themselves and in relation to 
spermatogenesis and polar cells. 
I. Potar GLopuLEs AND Extrusions FRoM REPRODUCTIVE CELLs. 
(1) We1smann.—‘ Die Continuitaét des Keimplasmas,’ 1885, chap. ii, “ Die 
Bedeutung der Richtungskérperchen,” vide Nachschrift. 
(2) Barpran1.—* Contribution A l’Etude dela Formation des Organes Sexuels 
chez les Insectes,” ‘ Rec. Zool. Suisse.,’ T. ii, 1885. 
(3) Sapatrer.—* Contribution a l Etude des Globules polaires et des elements 
climinées de lceuf en general” (Theorie de la sexualité), Montpellier, 
1844. 
VOL. XXVI, PART 4,—NEW SER. RR 
