600 Wisconsin Academy of Sciences, Arts, and Letters. 
chromosomes found in the nuclei of various insects by Henking 
(40), Montgomery (60, 61), Sutton (10,1), Paulmier (76), de 
Sinety (92) and others, have been shown to be as constant nu¬ 
clear elements as the ordinary chromosomes. 
For plants the work of Strasburger (95, 96), Miyake (55), 
and Miss Sykes (102) on Funkia, of Rosenberg (79) on Lis- 
tera ovata, of Miyake (55) on Galtonia and of Muller (68) 
on Yucca has shown that a constant difference in the size of the 
chromosomes exists in these species. Miiller further reports 
that the small chromosomes in Yucca lag behind in the ana¬ 
phase and go into the resting condition on the side of the 
daughter nucleus toward the equatorial plate and that in the 
following prophase they reappear in the same position from 
which they had disappeared. 
More recently the discovery of the so-called prochromosomes 
of Rosenberg and Overton in the nuclei of certain species has 
given no little support to the doctrine of the individuality of 
the chromosome. These bodies occur in the nuclear reticulum 
as persistent conspicuous chromatic masses of the sarnie num¬ 
ber as the chromosomes and v§ry from a nearly spherical form 
in some of the Cruciferae to an elongated rod-like structure in 
Thalictrum and Calycanthus. The persistence of these cen¬ 
ters about which the chromatin of the reticulum is aggregated 
in the prophases has enabled Overton (74) to follow, the course 
of the chromosomes of Thalictrum and Calycanthus through 
the reduction divisions and to observe that these centers, at 
least, retain their identity throughout. Overton has reviewed 
the literature of this subject fully. 
Fick (27) regards the chromosomes as not persisting from 
one cell generation to the next but changing in composition as 
the ranks of a maneuvering army may change from: day to day 
without changing the composition of the army. 
The work of Hacker (36) and of Riickert (81) on Cyclops 
demonstrated that in these forms there is no fusion of the 
paternal and maternal chromosomes in fertilization. For a time 
at least the two sets of chromosomes remain separate and distinct 
and appear as separate groups in metaphase. Their work has 
