646 The American Naturalist. [August, 
nucleus, these are called the archoplasmic filaments by Boveri, 
since they proceed from what is now believed to be the 
dynamic element, the archoplasm (fig. 8). As the activity 
becomes more intense the filaments are seen to diverge from a 
centre—the archoplasmic centrosome—which lies just without 
the nucleus at either pole; this radial display of cell-forces 
suggested the term “asters” to Fol, and “spheres attractive ” 
to Van Beneden. The behavior of the chromatin, or heredi- 
tary substance, under these archoplasmic forces, is beautifully 
shown in Carnoy’s diagrams (fig. 7). First, the nuclear wall 
—Arter Division, INTERI F A DAUGHTER-CELL IN THE Squip. (After Watase.) 
Division has just taken place and the daughter, N, shows the chromatin coil. The daughter 
is just forming two new centrosomes, A-A, by direct division. 
breaks up, then the chromatin coil unfolds into lines of verti- 
cal striation which become thread-like, hence the term mitosis, 
and then more compact, until finally a number of distinct 
vertical rods, chromatin rods, or chromasomes are formed. 
A remarkable and significant fact may be noted here, that 
the number of chromasomes varies in the cells of different 
species, and even in the cells of different varieties (as in the 
thread-worm of the horse—Ascaris megalocephala), but is con- 
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