CLASSIFICATION OF TISSUES. 19 
Describe the direct method of division. 
The nucleus divides into two parts by a simple process of constric- 
tion. The cell-body divides in the same way, each part of the ccil- 
body appropriating a nucleus to itself. 
Describe indirect cell division or karyokinesis. 
The intranuclear network becomes converted into a convoluted 
thread, changing to a rosette or wreath, then forming a star or aséer, 
the centre of which is the centre of the nucleus. 
The nucleus now becomes oval. The rays of the aster collect around 
points at the ends or poles of the nucleus, and form the diaster. 
The centre of the nucleus is now called the equator. Next it 
divides through the equator, and by a reversal of the process each 
part becomes a daughter nucleus. The protoplasm changes and be- 
comes divided at about the same time that the nucleus separates. 
What are the vital properties of all cells ? 
Nutrition, growth, function, and reproduction. 
CLASSIFICATION OF TISSUES. 
How are all embryonic cells formed ? 
By division and subdivision of the ovum. 
After a large number of cells are formed how do they arrange 
themselves ? 
Into a membrane called the blastoderm. 
Describe it. 
It is composed of two portions. First, the Archiblast, whick is 
divided into three layers, the Epiblast or outer layer, the Mesoblast or 
middle layer, and the Hypoblast or inner layer. The other portion of 
the blastoderm is called the Parablast and fills up the interstices of 
the mesoblast. Its origin is uncertain. 
Of what elementary tissues is the human body composed ? 
The Epithelial Tissues. 
The Connective Tissues. 
The Muscular Tissues. 
The Nervous Tissues. 
From what layers of the blastoderm are these different tissues 
produced ? “ 
Of the archiblastic layers the epiblast gives origin to the epithel- 
ium of skin and adnexa, to the epithelium of the terminal portions of 
