K. R. Lewin 
261 
All trace of distinction between protoinerite and deutonieiite is soon 
lost, and the cyst is occupied by two masses of protoplasm separated by 
an equatorial septum. The spherules fade, but what the fate of their 
colourable material is, I am unable to say. They lose chi’omatin until 
they are ver}^ little darker than the kai’yolymph (PI. XVIII, figs. 9, 10). 
They are usually present now to the number of six or more, though 
I have not been able to find out how the increase is effected. 
Apparently concurrently with this—no connection is suggested— 
some process of chromidiation goes on, which results in the ectoplasm 
becoming faintly chromatic, and taking on a dark grey tone in Heidenhain 
preparations. This chromidiation has no connection with the formation 
of gamete nuclei, and a similar occurrence is not unknown in other 
gregarines (PI. XVIII, figs. 9, 10). 
At length the impoverished trophonucleus gives rise to the segmen¬ 
tation nucleus. PL XVIII, fig. 11 shows the old nucleus and the first 
spindle, the latter cut rather oblhjuely. The trophonucleus still contains 
a certain amount of chromatin, but no spherules are visible, and the 
nuclear membrane has disappeared. How the achromatic spindle is 
formed has not been ascertained, but from figs. 12 and 12 a it is fairly 
evident that the chromatin of the segmentation nucleus has been drawn 
directly from the trophonucleus. Attention is especially directed to the 
faint, grey-staining limb projecting from the trophonucleus to the spindle 
(PI. XVIII, fig. 12). 
The disorganised trophonucleus disappears, how quickly I am unable 
to say. 
The further development within the cyst follows the normal type. 
By successive mitoses (figs. 13, 14) a large number of nuclei are formed, 
and these ultimately lie for the most part near the surface of the 
cytoplasm. I have not found any suggestion that reduction divisions 
occur immediately before gametogenesis, but the material is unfavourable 
for investigating this point. 
Formation of Gametes. 
This has been followed in vivo. Within the cyst-wall, the surface of 
the protoplasm becomes lobulated (Text-fig. 3). The line of separation 
between the individuals still persists. The lobulation becomes extreme, 
and at length the gametes arise from the surface as little ovoid pro¬ 
trusions (Text-fig. 4, a). They ultimately get cut off from the residuum 
(Text-fig. 4). There is a slight difference in size between the gametes 
arising from one sporout and those arising from the other in the cyst 
