‘ Heterotypical Reduction ' in Somatic Cells . 799 
senting their four ends to view in the same plane ; or else to that of 
chance apposition of two pairs of chromosomes, an arrangement seen fre¬ 
quently on normal equatorial plates, as was pointed out by Strasburger 
(Fig. 28). The marked longitudinal fission of the chromosomes seen also 
as early as the spireme thread stage—noted above as characteristic of 
chloralized tissue—is not really comparable to the condition seen in the 
tetrads of sporogenous tissue. It is frequently conspicuous in diasters con¬ 
taining twice the somatic chromosome number. But though it must in such 
figures represent a premature fission of the chromosomes of the daughter 
nuclei, yet no previous heterotype pairing of chromosomes is entailed by it, 
as is obvious from the number of the latter found on counting. 
Finally, the ‘ heterotype 5 figures are found in cells which still contain 
the tetraploid number of chromosomes. This last point appears to be 
conclusive evidence of their non-reducing character. In the cell shown in 
Fig. 26, each of the twenty-eight double chromosomes is markedly hetero¬ 
typical in character ; yet it is scarcely to be supposed that the cell in question 
can have contained more than twenty-eight pairs of chromosomes, which 
number already is twice that in the normal somatic nucleus. Since, then, 
there has been no reduction, the figures must owe their heterotypical 
character to some other factor than that of the pairing of chromosomes. 
Consideration of the above points of evidence suggests that this factor 
is a chemico-physical one, and that the stumpy heterotypical figures in the 
pea are to be explained as due to the occurrence of swelling and massing 
together of its normally short, thick chromosomes under influence of the 
chloral hydrate. It has been noted above that, as in the pea, so also in Galtonia 
and the bean, there is, after treatment with chloral hydrate, an evident altera¬ 
tion in the consistency of the chromatin, which becomes swollen-looking, 
granular, and massed together. The chromosomes of these plants are so long 
and thin, however, that a very considerable degree of contraction would be 
necessary to make them resemble heterotypical figures, whereas in the pea 
very little would effect this. Fig. 27 is of note as showing the emergence 
of the ‘ heterotypical * chromosomes directly from the coiled spireme ; it 
should be remarked in connexion with it, that the entire absence in the 
root tissue of anything like a synaptic stage is another point of evidence 
against the true heterotypical nature of these chromosomes. 
Great importance is attached by Nemec, in his arguments for the 
occurrence in root tissue of heterotype reduction, to the disappearance of the 
tetraploid cells from the chloralized root-tips. He particularly emphasizes 
this point in his most recent paper. In this he states that complete dis¬ 
appearance of these cells occurs in lateral roots, which, if examined at an 
earlier fixation, are seen to contain them in considerable numbers. It has 
not been possible to repeat these last experiments in detail. The dis¬ 
appearance of the tetraploid cells from the roots in question would seem, 
