346 
AMERICAN JOURNAL OF BOTANY 
fVol. io, 
to be compound, but do not find a definite number of the bodies that he 
defines as chromioles. O. Hertwig (1906) applied the term chromiole to the 
Scheibchen of Chironomus nuclear filaments. 
The shape of the chromomeres varies from spherical to oval, to cubical, 
with or without rounded edges and corners, and finally to irregular. As 
generally found, they are doubtless aggregates and are made up of smaller 
elements which again may be found subdivided into varying grades of 
smaller particles. It has been generally held (Mottier, 1907, p. 336; Miyake, 
1905; and others) that these chromomeres are not the ultimate units of the 
chromatin itself. Strasburger says: 
Eine Ide ist wie wir sahen, nicht der letzte der im Kern festzustellenden Strucktur- 
elemente; sie geht aus der Vereinigung kleiner Gebilde hervor (1905, p. 53). 
Conversely, then, as I consider it, the ultimate chromatic particles 
agglutinate into groups, these unite to form an aggregate of groups, and 
the group aggregates unite to form a chromomere. The whole process 
may be a series of successive agglutinations which involve, in the first 
instance, the migration of the minute particles through the homogeneous 
matrix ( Zwischensubstanz ) of the chromosome, i.e., the linin. 
The term Id has been avoided because it is not desired to associate 
these bodies with Weismann’s (1885) conceptions, nor indeed is it intended 
to identify the chromomeres as described with any of the theoretical loci 
recently developed in the genetical field (see Mottier, 1907, p. 336). 
I consider the unit of these agglomerates to be the ultimate microscopic 
chromatin particle as observed usually in fixed material , and as discussed 
by Wilson (1900, p. 37). Meyer (1920) has recently formulated the most 
specific hypothesis yet advanced as to the ultimate ultra-microscopic 
composition of the chromatin and cell contents. He assumes as essential 
constituents of the cell at least three types of so-called Vitiile, cytoplasmic 
vitules, nuclear vitules, and trophoplasmic vitules. These vitules are also 
extremely complex and are assumed to be made up of so-called mions. 
The mass of an electron is said to be 2,000 times smaller than that of a 
hydrogen atom. Meyer assumes the mion to be 2,000 times smaller than 
the electron. I shall take up this point in another paper. 
In the mother cells, the linin appears to be distinct in composition from 
the linin of the achromatic spindle, since, in preparations stained with 
aceto-carmine, it appears rather dense and of a most delicate straw to 
rose color, whereas no element of the achromatic spindle is either stained 
or perceptible. On the other hand, in preparations of the stamen hair, 
the elements of the achromatic spindle are clearly visible both in stained 
and in unstained material but only between anaphase and telophase. The 
surfaces of the Zwischensubstanz are clearly marked, not only by a very 
delicate color differentiation, but also by their relative refractive indices. 
How many grades in size there may be in the subdivision of the chromo¬ 
mere is not clear. Figure 8, Plate XXIX, figures the construction as seen 
