138 
Thos. H. ]\Iontgomery, jr. 
mode of conjugation of the chromosomcs must liave their origin in the 
clianges of the synapsis stage, and it is in this important stage tliat varia- 
tions may perliaps be most freqnently engendered. 
6. Finally we may consider what relation tliere may be between the 
first kiiid of Variation, that of the s-chromosomes, and the dimegaly of 
the spermatocytes; that is, whether the larger sperniatocytes exliibit 
more or less Variation of the chromosomes than do the smaller spermato- 
cytes. Such chromosomal Variation was fonnd in spindles of the first 
maturation mitosis in follicle 1 in 34,3% of 35 cells; in follicle 2 in 21,8° o 
of 55 cells ; in follicle 3 in 20,8% of 53 cells ; in follicle 4 in 7,6% of 79 cells ; 
in follicle 5 in 4,6% of 109 cells ; and in follicle 6 in 4,7% of 64 cells. These 
cells were from all the particnlar six testes described above. Thus the 
largest spermatocytes (of follicles 1 and 3) and the smaUest (of follicle 2) 
exhibit the greatest amount of Variation (20,8% to 34,3%) whüe the 
spermatocytes of intermediate size (from follicles 4 — 6) show much less 
Variation (4,6% to 7,6%). ln other words, the best nourished and the 
least nourished ceUs possess the greatest amount of chromosomal Varia- 
tion. It is then perliaps permissible to concliide, if we may rely npon 
such small figures, that chromosomal Variation may stand in soriie Con- 
nection with the tropliic environment, and therefore Variation in general 
be due ultimately to external Stimuli. 
V. Paolo Deila Valle’s Views on Chromosomal Variation; and the 
Continuity of the Chromosomes. 
Paolo della Valle^) has recently expressed conclusions on Varia- 
tion in chromosomal nnmber that are so diametrically opposed to my 
own, that his ^^ews may fittingly be reviewed at this place. 
His main conclnsion is that: „The cliromosomes should be considered 
as temporary and variable organizations of chromatin, which form in the 
prophase and dissolve in the telophase”, which do not continue as enti- 
ties from one mitosis to another, and the nnmber of which is consequently 
snbject to individual fluctuation. Their nnmber according to him is 
simply the quotieut of the qiiantity of chromatin and the average size of 
the chromosomes, and the normal numerical A'ariability is a reflection of 
the Organization of the chromatin; by „Organization” is meant the com- 
plex of granulös that comjiose the chromatin. Increase in the nnmber 
L’Organizzazione della Cromatina studiata mediante 11 Numero dei Cromo- 
somi. Arclxiv. Zoologico. 4. 1909. 
