Osborn. — Spongospora sublerranea , ( Wallroth ) Johnson . 331 
other of the nuclear divisions. Maire and Tison 1 and Prowazek 2 record 
these in Sorosphaera and Plasmodiopkora , and the former regard this type 
of nuclear division as an ‘ intranuclear karyokinesis combined with an 
amitosis a statement which is in accordance with their advocacy of the 
‘ dual hypothesis ’ of nuclear structure. 
Reproductive phase — akaryote stage . When the amoebae have exhausted 
most of the food material in the cell (though the host nucleus and occasional 
starch grains are still to be seen at this stage), they coalesce to form a 
plasmodium (Fig. 5). The plasmodium is thus the product of the fusion of 
a number of vegetative amoebae, and this fusion Is the first step to spore 
formation. It would seem to be usual for only one plasmodium to form in 
a cell, though exceptions are to be found, and in one case as many as eight 
mature spore balls were seen (Fig. 16). 
The formation of the plasmodium is followed by an akaryote condition 
in which the nuclear matter appears to be scattered throughout the whole 
plasmodium. The chromatin granules on the network, hitherto a prominent 
feature, disappear in all the nuclei of a plasmodium at the same time, being 
possibly conducted to the nuclear membrane along the linin threads and 
there extruded. In the same way the karyosome diminishes in size and is 
gradually lost (Fig. 19), while the protoplasm of the plasmodium (now 
rounded in shape wherever conditions of space permit) becomes filled with 
deeply staining granules which may be termed chromidia. This appearance 
is shown in Fig. 7, which is a drawing of a plasmodium at this stage. It 
will be seen that the sites of the nuclei are not lost to view, but remain as 
circular areas free from any trace of chromidia and showing up in marked 
contrast to the surrounding protoplasm. This appearance might at first 
sight be thought to be suggestive of vacuolation ; the nuclear areas, how- 
ever, when examined in sections stained with iron haematoxylin and light 
green for instance, are perfectly distinct. A similar occurrence is recorded 
for both Sorosphaera and Plasmodiophora, while a chromidial state is well 
known for certain Protozoa. 3 It is impossible to give any idea of the time 
of duration of the akaryote condition, but to judge from my preparations 
I do not think it to be very long. 
The nuclei as they are developed the second time are of a very different 
appearance from the previous vegetative ones. There is a membrane, net- 
work, and chromatin granules staining an intense black with haematoxylin, 
but no karyosome. It is not easy to trace the development of the new 
nuclei, but there is evidence that they are constructed de novo, rather than 
reconstituted on the sites of the old ones. The evidence for such a state- 
ment rests on such stages as are figured in Figs. 8 and 20. By the side of 
the clear spaces, representing the previous vegetative nuclei, there may be 
1 Maire, R. , and Tison, A. : loc. cit., p. 230. 2 von Prowazek, S. : loc. cit., p. 398. 
3 See literature quoted by Dobell, C. C. : Q. J. Micro, ScL, vol. liii, N. S., 1909, p. 279. 
