6 GERM-CELL CYCLE IN ANIMALS 
the properties of each and a number of properties 
peculiar to itself. No doubt the protoplasm differs 
in its physical nature in different cells. In the egg 
of the starfish, Asterias, Kite (1913) has shown that 
the cytoplasm is a translucent gel of comparatively 
high viscosity and is only slightly elastic; pieces 
become spherical when separated from the rest of 
the egg. Scattered throughout this gel are minute 
granules (microsomes) about 755 mm. in diameter 
which cannot be entirely freed from the matrix. 
What appear to be alveoli contain globules which 
possess many of the optical properties of oil drops; 
these are suspended in the living gel. The cyto- 
plasm of the starfish egg is not therefore alveolar in 
structure as usually stated, but is rather of the 
nature of a suspension of microsomes and globules 
in a very viscous gel. The nuclear membrane is a 
highly translucent, very tough, viscous solid, and 
not a delicate structure as ordinarily conceived. 
The nucleolus is a quite rigid, cohesive, granular gel 
suspended in the sol which makes up the rest of the 
nuclear material. Dividing male germ cells of cer- 
tain insects (squash bugs, grasshoppers, and crickets) 
revealed the fact that the chromosomes are the most 
highly concentrated and rigid part of the nuclear 
gel; that the spindle fibers are elastic, concentrated 
threads of nuclear gel; and that the metaphase 
spindle fibers seem to be continuous with the ends of 
the chromosomes. 
The ground substance of the nucleus is a sol termed 
nuclear sap or karyolymph. In the so-called ‘rest- 
