British Association. 
1S79.] 
631 
non probably connected with the absorption of nitrogenous 
matter. 
That there is no essential difference between the protoplasm 
of plants and of animals is rendered plain by a number of motor 
phenomena which we have been in the habit of erroneously re- 
garding as peculiar to animals. All living protoplasm alike 
possesses the property of resisting the entrance of colouring- 
matter into its substance, though as soon as dead it can be 
coloured throughout. 
Recent researches on the division of animal cells show how 
close is the agreement between plants and animals in all the 
leading phenomena of cell-division, and afford further proof of 
the essential unity of the two great organic kingdoms. The egg, 
as a typical cell, distinguishable by no tangible characters from 
thousands of other cells, is nevertheless destined to run through 
a definite series of developmental changes which have as their 
end the building up of an organism like that to which the egg 
owes its origin. It is obvious that such complex organisations 
as thus result can be derived from the egg-cell only by a process 
of cell-multiplication. The birth of new cells derived from 
the primary cell or egg thus lies at the basis of embryonic deve- 
lopment. It is here that the phenomena of cell-multiplication 
in the animal kingdom can be most successfully observed. 
The President then briefly described the so-called “ cleavage ” 
of the egg, which is merely a multiplication of the egg-cell by 
repeated division. The egg has its protoplasm and its’ nu- 
cleus, and is, as a rule, enveloped in a delicate membrane. The 
protoplasm forms the vitellus or yolk, and the surrounding mem- 
brane is called the vitellary membrane. The division about to 
take place is introduced by a change of form in the nucleus, 
which assumes the shape of a spindle precisely as in the cell- 
division of plants. On each pole of the spindle transparent 
protoplasm collects, forming here a clear spherical area. Each 
pole of the spindle has become the centre of a system of rays, 
which stream out in all directions into the surrounding proto- 
plasm. The protoplasm thus shows enveloped in its mass two 
sun-like figures, whose centres are connected to each other by 
the spindle-shaped nucleus. To this, with the sun-like rays 
streaming from its poles, Auerbach gives the name of “ Karyo- 
litic figure.” A phenomenon very similar to what occurs in cell 
division among plants now shows itself. The nucleus becomes 
broken up into a number of filaments which lie together in a 
bundle, each filament stretching from pole to pole of the spindle. 
In its central point each filament shows a knot-like enlargement, 
and from the close approximation of the knots there results a 
thick zone of protoplasm in the equator of the spindle. Each 
knot soon divides into two halves, and each half recedes from 
the equator and travels along the filament towards its extremity. 
When arrived at the poles of the spindle each set of half knots 
