5i6 



JOHNSON. 



[Vol. VIII. 



The remarkable metamorphosis undergone by moniliform 

 and rod-shaped meganuclei at time of fission appears to be 

 purely a change of form. As stated on a preceding page, I 

 have not been able to detect the least structural alteration in 

 the substance of the meganucleus at any stage. Perhaps the 

 most obvious explanation of the changes is, that an equal 

 division of the meganucleus in its moniliform, or cord-like, 

 flexuous state is not easily brought about, owing to its spiral 

 disposition in the body and the frequently unequal size of its 

 nodes. The case is different when the nucleus divides after 

 having returned to the moniliform condition, for the nucleus 

 is then nearly straight, its middle point coincides with the 

 plane of division, and the nodes, newly formed from a cylin- 

 drical rod of even diameter from end to end, are very nearly 

 alike in size. That the division is fairly equal is evinced by 

 the fact that the number of nodes in each daughter-stentor is 

 usually about the same, as the following table will indicate : — 



It is seen that in eleven instances out of the twenty-two given 

 the number of nodes in each daughter-nucleus is exactly the 

 same ; in four other cases there is a difference of only one 

 node. In 68 per cent, then, of the specimens examined, the 

 division is fairly equal. But how shall we account for the four 

 instances (pairs 19-22) of decidedly unequal nuclei.'* I believe 



primitive type — a reminiscence of the time when the nucleus was always spherical. 

 The transient appearance of a constriction about the nucleus (Fig. 41 b-e), whether 

 it divides at this time or later, lends strength to this view; for on this basis we 

 must regard it as an inherited tendency to division. 



