PROGRESS OF MICROSCOPICAL SCIENCE. 35 
view which derives the former from cells of the epiblast, as against 
that which would assign to it a hypoblastic origin.” 
In conclusion, it may be observed that Mr. Schafer finds that 
Hensen has also observed this structure. 
The different Sexuality of Volvox globator and V. minor.—This im- 
portant subject has been investigated by M. L. F. Henneguy, who read a 
paper before the French Academy in July last. This paper is abstracted 
at some length by the ‘Academy. It states that M. Henneguy de- 
scribes Volvox minor as dioicous, while the V. globator is monoicous ; 
and its reproduction has been recently described by Cohn.* The 
dioicous volvox is a colony of unicellular alg, each member being 
furnished with two vibratile cilia, and all disposed regularly in the 
gelatinous wall of a hollow sphere. M.Henneguy finds four kinds of 
these colonies, which he calls cenobiums: 1, containing only vege- 
tative cells, and having young ccenobiums in their interiors, each 
derived by division and multiplication of a vegetative cellule; 2, a 
great number of these cenobiums which contain, likewise, male 
elements, androgonidia, situated in the thickness of the gelatinous 
wall; 3, those which exhibit only vegetative cells and androgonidia, 
and not producing any daughter colonies ; 4, female ccenobiums which 
contain only gynogonidia, or oospheres in the interior of their spheres. 
The androgonidia are formed at the expense of a vegetative cell 
which acquires a larger volume than the rest, and divides into 
parallel segments, each having the form of an elongated cone with 
its thickest end green, and the other one transparent with a little red 
point, and two vibratile cilia. The bundle of antherozoids exhibits a 
continual oscillation in the antheridium. The gynogonidia spring 
likewise from a differentiation of a vegetative cellule, which grows 
much larger than the androgonidia, and becomes full of starch and 
chlorophyll granules, giving the oospheres a dark-green aspect. At 
the moment of fecundation the bundles of antherozoids are set at 
liberty by the dissolution of the antheridia wall; they move quickly 
through the water, and fix themselves on the female ccenobiums, and 
then separate to fecundate the oospheres, but the author was not able 
to observe the exact moment of their penetration. After fecundation, 
the oospheres surround themselves with a thick membrane having a 
double outline, which was not previously visible, and rapidly change 
colour, passing from dark green to yellow green, and then to orange. 
They then contain a red oily matter and a larger quantity of starch. 
This orange coloration made some observers suppose it was a separate 
species, the V. aureus, Ehr. These volvocina, male, female, and 
neuter, seek the light and keep near the surface of the water; but 
when the female colonies are fecundated they get away from the 
surface. In a glass vessel the green ones will be seen on the side of 
the light: the others on the opposite side. If the vessel is turned 
round they change places, and the orange ones fly from the light 
quicker than the green ones seek it. When these objects first appear 
in the waters where they are formed, scarcely any but neuter colonies 
* « Beitrage zur Biologie der Pflanzen,’ 1875. 
