THE STRUCTURE OF PROTOPLASM 297 
germ plasm or heredity by saying that the fluctuating behavior of the 
visible characters is explained by modifying factors in the germ plasm is a 
preformationism which would have put even Bonnet to the blush. My 
point is here that at every step the possibilities of the structure of the germ 
plasm as well as the visible behavior of characters must be kept in mind. 
Perhaps the most obvious weakness of all these theories of units of 
protoplasmic structure and unit factors in heredity is that they carry in 
them the vices of the old preformationism. They seem too much like 
attempts to explain visible and familiar complexity by the assumption of a 
parallel complexity in the germ plasm, and this in spite of the generally 
admitted incommensurability of cell organization and metaphyte organiza- 
tion. Driesch, with all his tendency to mysticism, must be credited with 
having recognized and made clear that the facts of nuclear and cell division 
and the resulting perpetuation of the hereditary complex make it impossible 
to assume a spatial configuration of the germ plasm in three dimensions 
parallel to that of the many-celled organism as a whole. The theory of 
multiple unit factors attempts to maintain in lesser degree this same parallel- 
ism — with the added difficulty that the germ plasm which is to be equa- 
tionally divided must even contain a number of unit factors for each char- 
acter of the organism. 
It is of interest to note in connection with these hypotheses of particulate 
structure in the protoplasm the available data as to the size of the various 
elements involved. 
Human blood corpuscles 7, 500 micro m 
Anthrax bacillus 4,000-5,000 micro /j, 
Cocci 500-1,000 micro M 
Chromosome : 
Primula Kewensis with 18 chromosomes 
(Farmer) 1,262 X 1,110 micro m Vol. .8141 cubic n 
Primula Kewensis with 36 chromosomes 
(Farmer) 1,022 X 874 micro ix Vol. .4088 cubic ix 
Chromosome from macromere of Crepidula 
(Conklin) Vol. 5.2 cubic /* 
Chromosome from micromere of Crepidula 
(Conklin) Vol, 2.6 cubic fx 
Granules of central body (Marquette mss.). . . .300-500 micro n 
Smallest gold particles observed in hydrosols. . . 6-15 micro 
The same in non-permanent suspensions 75-200 micro /x 
Molecule of soluble starch (Lobry de Bruyn). . . 5. micro fx 
Haemoglobin molecule 2,5 micro 
Casein molecule 2.4 micro ix 
Chloroform molecule (Jager) 0.8 micro ix 
Alcohol molecule 0.5 micros 
Hydrogen molecule (O. E. Meyer) o.i micro n 
The granules of the central body which relate themselves so conspicu- 
ously to spindle formation are perhaps of the same order of magnitude as 
