CHROMIDIA AND THE BINUCLEARITY HYPOTHESES. 311 
Such speculations, to my mind, greatly exceed the limits 
of legitimate inference. Yet it has come to be the fashion 
of late to repeat that a binuclearity of this kind exists in all 
accurately-investigated Protozoa (e.g. Hnriques, etc.). 
One of the most striking pieces of evidence in favour of 
somato-generative binuclearity is seen in the life-history of 
the remarkable infusorian, Ichthyophthirius (Nere- 
sheimer, 08). The nucleus (amphinucleus) buds off a smaller 
nucleus, which divides into two. The latter then undergo 
two reduction divisions each, and finally fuse—thus enacting 
an autogamy. The zygote nucleus then re-enters the original 
nucleus and so reconstitutes a fresh amphinucleus (text-fig. 
TpxtT-FIG. 22: 
Ichthyophthirius. 
A. The originally single nucleus gives off a micronucleus. 
B. The micronucleus undergoes two divisions. Three of the 
four resulting nuclei degenerate—the fourth divides once 
more (spindle). 
C. The spindle gives rise to a pair of nuclei which fuse (auto- 
gamy). 
D. After fusion, the nuclei re-enter the original nucleus and 
fuse with it. 
(After Neresheimer, ‘O08—schematic.) 
22). It certainly appears as though we were here dealing with 
two different kinds of chromatin—trophic and gametic— 
united into one nucleus. 
Kntamceba coli also seems to furnish strong evidence in 
favour of this view. In neither of these cases, however, is 
the evidence conclusive, and both stand in need of con- 
firmation. 
The second binuclearity hypothesis—which has, to a 
considerable extent, been confused with the one already 
discussed—is more properly so-called, for it has, as its basis, 
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