388 MITCHEL CARROLL 
I at first thought that the count was probably constant for 
this animal, but on examining some growth stages and first 
spermatocyte prophases, a precocious dyad (in addition to the 
accessory) was discovered in two cysts. Although it was diffi- 
cult to secure accurate counts in these cysts, I think each complex 
consisted of eleven tetrads plus the accessory, plus one dyad. 
B. Analysis of the counts 
In the germinal complexes of each of five (nos. 950, 980, 2511, 
2525 and 2526) atypical individuals, there is constancy neither in 
the number of chromosomes nor in the amount of chromatin. 
It is evident (counts given for no. 950, tables 1, 2, 3, and 
pls. 1, 3, 4, 6, 7, 8, 9, 10, 11, 12, 18, and 14) that the variations 
in the composition of the chromosome group are due to the pres- 
ence of extra or supernumerary elements. No complex was 
found, which has less than the normal number of chromosomes 
for its cell generation. 
In all spermatogonial metaphases there are at least twenty- 
three dyads constantly present; in all first spermatocyte meta- 
phases there are (with one apparent exception, illustrated in fig. 
10, due to a premature division or failure of pair no. 10 to synapse) 
at least eleven tetrads and one accessory (a dyad) ; there are never 
less than eleven dyads in a second spermatocyte metaphase. 
These are the numbers characteristic of the several germ-cell 
generations of the animals which manifest no departure from the 
typical or normal chromosomal organization (pls. 2 and 5). 
The numerical variations in the spermatogonia are due to the 
presence of from one to three dyads in excess of the typical 
number. Variations in the first spermatocyte counts are also 
clearly due to extra elements which may be for any given com- 
plex, a dyad, a tetrad, or a dyad and a tetrad. (In three cells 
there are two extra dyads present.) 
In the second spermatocyte metaphases the departures from 
the normal numerical organization are the result of the presence 
of from one to possibly three extra dyads. Although in each of 
two cells (figs. 114 and 117), to be discussed later, the aberrant 
count is due to the presence of a monad. 
