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POPULAR SCIENCE REVIEW. 
tube of viviparous Aphides, Balbiani saw lying’ in a group of 
cells a large central one, which he states to be mother of all the 
future ovules. The sole function of this central cell is to bud 
off fresh ovules. The peripheral cells are attached to the 
central cell by tubular pedicles, and their function is to nourish 
the mother-cell. 
The ovules derived from this mother-cell present, as they 
pass from the end chamber into the tube, a distinct germinal 
vesicle , whose disappearance is quickly followed by the formation 
of a blastoderm (cellular) which encloses the central yolk mass. 
The ovule now changes its shape from spherical to an 
elongated oval, the yolk mass within becomes granular, and is 
covered with a fine membrane. Next the enveloping layer of 
blastoderm gives way, by separation of its hitherto closely- 
packed cells at a point looking towards the free end of the 
tube. A portion of the internal granular yolk protrudes 
through the gap, and the vitelline membrane may be well seen 
at this moment inside the blastoderm envelope, but enclosing 
the central vitelline mass. The protruding portion of vitelline 
membrane and its contents now attaches itself to the epithe- 
lial lining of the ovarian chamber, the cells of which are 
hypertrophied, and there becomes engrafted. The ovule being 
thus temporarily fixed, the vitelline vesicle in the interior 
divides into two secondary nucleated cells, one of which is in- 
volved in the mass adhering to the tube, whilst the other re- 
mains in the interior. These cells are to be the source of the 
male and female elements of the future animal. Each of them 
becomes surrounded by a separate group of derivative cells, 
the group adherent to the epithelium of the tube representing 
the male, and that lying free in the interior of the blastoderm 
envelope constituting the female element — that is to say, the 
generative cells of the future ovules surrounded by their nutri- 
tive cells. The latter group divides into subordinate groups, 
over which new ovarian sheaths are subsequently formed. The 
generative vesicle of the male group continues its develop- 
ment, increases in size, and after forming connections with the 
female generative apparatus, constitutes a reservoir for the fe- 
cundative corpuscles, — becoming, in fact, a true seminal vesicle. 
Comparing this description with those of Leydig and 
Huxley, we observe, especially in the earlier part, such a 
similarity of observation as affords warranty for the correct- 
ness of all that follows. The pseudo- vitellus of Huxley is the 
female group of Balbiani, the bond fide assurance of his obser- 
vation of nuclear or germinal spot being given by Balbiani.* 
* It is of course possible that Balbiani was not aware of Huxley’s inter- 
pretation of the anatomical facts. 
