1t0 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
In the case of unequal tetrads, however, variation in shape does 
have some meaning with reference to chromosomal organization. In 
the specimens of Phrynotettix which I have studied, the shape of 
tetrad B in two individuals is fundamentally different from that in 
the other eleven, because, in the latter, a definite part of one member 
of the pair is lacking. Similarly, in the case of Ci and C%, the difference 
concerns a definite part of the members of the pairs. But the im- 
portant thing to be kept in mind is that the organization of each of 
these tetrads is constant for any individual animal, and such differ- 
ences as exist between individuals can be readily accounted for. 
b. Persistent Organization of Chromosomes. 
1. The -selected chromosomes.— One of the most important con- 
clusions arrived at in the present study relates to the constancy in 
the finer organization of the chromosomes, both from stage to stage 
in the same individual, and from one individual to another. This 
is shown in two ways: — first, by the existence in chromosome-pair 
B of an architecture that is constant both for any one individual in 
the various stages in which any architectural condition could be 
recognized, and likewise for all the individuals studied; secondly, by 
that of a particular pair of chromosomes (A) recognizable through all 
the stages from spermatogonia to spermatids, the recognition being 
made possible by the fact that the chromosomes in question possess 
properties which are characteristic and constant for all stages. 
Both of these selected chromosomes, A and B, tend to stain more 
deeply than the other autosomes, but this tendency is much more 
marked in A than in B. If chromosomes possessing similar peculiari- 
ties be found in related species, may they not be regarded as homolo- 
gous to the selected chromosomes A and B of Phrynotettix? I think 
such homologies could be established. Miss Carothers (’13) shows 
that the small unequal tetrad in Brachystola is usually associated 
with the accessory chromosome, and is more intensely stained than 
_ the other autosomes. Might it not be possible to analyse this un- 
equal element in Brachystola and determine its relation to the unequal 
tetrads of Phrynotettix? Since these two genera are closely related, 
I believe this would be possible. Furthermore, the other unequal 
tetrads described by Miss Carothers for Arphia and Dissosteira were 
among the small chromosomes and, on account of the similarity in 
behavior, might be found homologous to B or C of Phrynotettix. 
