On tlie Dimegalous Sperm and Cliromosomal Variation of Euschistus, etc. 129 
cyte (fig. 18, PL IX) is many tiines tlie size of a spermatogonium (fig. 16) 
the difference in volume betweeii the univalent chromosonies of the two 
is very much less; in making the comparison between the chromosomes 
of these two cells the reader will recall that one half of any bivalent ele- 
ment of the spermatocyte is to be compared wdth a single element of the 
spermatogonium. After a mitosis mEuscTiistus each danghter chromosome 
grows to the size of the mother chromosome, biit grows no more than that 
or oiily little more. In accord with this is the well known fact that the 
sperm introduces into the egg chromosonies of the same size, and of equal 
total mass, as those present in the matured egg, though the egg is many 
times greater than the sperm. An enzyme possesses among other pro- 
perties the power of engendering changes in its medium while stiU preser- 
ving a constant mass. Of all the larger cellular compounds that we know 
the chi'omosomes agree most closely with this definition, and by reason 
of this constancy of mass alone miglit be considered enzyme masses. 
Chromosomes effect a most active metabolism during the growth period 
of the gerni cells, yet at the end of this period, in the fh'st matm'ation 
spindle, are not greatly different in volume from what they were at its 
commencement. The mass of the karyolymph, linin, cytoplasm and mito- 
chondria is readily changed by the degree of nutrition, the totality of tlieir 
mass is also much greater, wherefore it is probable they play a minor 
part in metabolism and consequently in inheritance. 
III. Chromosome Variation in Euschistus sp. 
The questions to be determined are the following: 1. is there any 
Variation in the number or behavior of the chromosomes in cells of the 
same generation of the same individual ; and if so, 2. does such Variation 
speak for or against the theory of the individuality of the chromosomes? 
In the fh’st place we need recall the normal or usualcourseof thesper- 
matogenesis, according to my previous account (1906). E. B. Wilson^) 
has emended my earlier observations (1898, 1901) in one respect, whith 
regard to the behavior during the maturation mitoses of the pak of niodi- 
fied chi'omosomes. Wilson called these bodies „idiochromosomes” ; I 
proposed (1906) to call the ordinary chi'omosomes „autosomes”, and the 
modified ones „allosomes”; and such allosomes as occur in pairs during 
the spermatogenesis I proposed to terni „diplosomes”; this terniinology 
will be followed in the present paper. The normal process is as follows. 
There are 14 chromosomes in the spermatogonia, one of which is very 
1) Studies on Chromosomes III. Journ. Exper. Zool. 3. 1906. 
Archiv f. Zellforschung. V. 
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