Katharine Foot and E. C. Strobell 305 
culties and hold unshaken faith in a theory that must fall with the 
miscount of a single chromosome. 
Individuality of the Chromosomes.—The first step in discussing this 
point is to give a definition of one’s conception of the term Individuality, 
for this term has been very loosely employed. If we mean by “ Individu- 
ality of the Chromosomes” merely that we recognize certain character- 
istics of size and form in some of the chromatin units called chromosomes 
and that there is a frequent repetition of these forms during different 
stages of development, then we may claim that the chromosomes of 
Anasa tristis unqualifiedly support the theory of the “ Individuality 
of the Chromosomes.” But on the other hand, if by “ Individuality of 
the Chromosomes ” we claim their morphological continuity, that several 
or even only one of the chromosomes can be followed wninterruptedly 
from the spermatogonium to the spermatid, that even during the growth 
period the chromosome form is maintained, then we must say that in 
our preparations Anasa tristis supports in a very restricted sense, if at 
all, the theory of the “ Individuality of the Chromosomes.” 
If at any time during the growth period it can be demonstrated not 
only that the chromosome form is obscured but that in its place we find 
a very different, though equally definite, chromatic structure—chromatin 
granules, a chromatin reticulum or a chromatic skein, we have no right 
to assert that the chromosomes of the earler and later stages have re- 
tained their individuality intact during this period. 
Although in Anasa tristis it can be demonstrated that during the rest 
stage of the first spermatocyte the morphological identity of the chromo- 
somes is completely obscured, it can be demonstrated with equal clear- 
ness that among the eleven chromosomes which emerge from the resting 
first spermatocyte three forms are so conspicuous and are so often re- 
peated that as a rule they can be identified from the early first prophase 
to the telophase of the second spindle. These are the eccentric chromo- 
some, the microchromosomes, and the largest chromosome of the eleven 
which is typically cross-shaped. To these might be added the dense 
dyad described on p. 289, but this form is neither so distinctive nor so 
constant as the other three forms. 
The eccentric chromosome we have already traced from the very early 
prophase to the telophase of the second spindle. 
The microchromosomes are so conspicuous: in nearly all the photo- 
graphs of the three plates that it seems unnecessary to trace them through 
the individual photographs. We will draw attention later to certain 
exceptions in their form or size. 
22 
