1880. ] A Sketch of Comparative Embryology. 97 
living objects there was nothing but protoplasm. In accordance 
with this view this substance was called the “ Physical Basis of 
Life,’ under which name it has been much paraded before the 
public. Bya great many persons protoplasm is conceived and 
described as a “ simple mass of jelly.” By an easy illogic this 
phrase of the very ignorant becomes a demonstration that life is 
a mere property of matter—but that is no matter to us now. What 
does concern us, is that protoplasm is not a mere simple mass of 
jelly, but is certainly very complicated, perhaps so complicated that 
its constitution is beyond the power of human conception. One 
of the visible indications of the complexity of protoplasm, is, that 
it is nota continuous substance, but interrupted by vacuoles or 
cavities, which vary in size, shape and number. These cavities 
are usually round or oval. The protoplasmatic partitions between 
them form a complicated network. Sometimes the cavities may 
fuse together, by a breaking through of the partitions, in which 
case the network is reduced to a number of connecting threads. 
The cavities are not empty, but filled with various substances, 
sometimes liquid, sometimes solid, and differing in chemical com- 
position, as the protoplasm is from one kind of cell or another. 
For the contents of the vacuoles I propose the name enclosures, 
It will be seen that protoplasm forms only the network which 
Surrounds the other substances. This is an important fact, with- 
out knowing which, it is impossible to understand the formation 
of eggs, 
` Let us return to the nucleus. It has been asserted that therea are 
numerous animals (Monera, etc.) mostly microscopic, which consist 
solely of protoplasm without any nucleus, and also in some cases 
that the egg-cell ejects its nucleus, and then it is called a cytode. 
Now it has been shown that a very large proportion of these un- 
nucleated protoplasms (Protista) really have a nucleus, and are- 
unicellular animals or plants; therefore it is prodad/e that no pro- 
toplasm can live without a nucleus, that is to say without being — i 
Part of acell So also with the egg; it mash become probable that 
it never loses its nucleus. o 
The result of these discoveries is to reëstablish the full import- 
ance of the ce//, as the unit of animal and vegetable organization. _ 
Recent j investigations by Biitschli (No. 18) and Engelmann upon (ae 
! The reader must remember, however, that a number of minute organisms | exist in o 
Which no nucleus has been observed. Future <> will decide whether the ab- 
Sence of the nucleus is real or apparent. 
