208 
H. M. WOODCOCK. 
behaviour of the karyosome at different periods of the life- 
cycle. For instance, as regards the Coccidia, speaking 
generally it may be said that during the schizogonic, vege- 
tative phases, the karyosomatic chromatin becomes subdivided 
up, in a premitotic manner, amongst the daughter-individuals; 
on the other hand, as a rule, on the approach of the 
•sporogonic part of the cycle — frequently during gametogony 
or else early in the history of the zygote — the karyosome 
is mostly eliminated, a “ nuclear purification ” of the nnre- 
quired, trophic chromatic material taking place.^ Moreover, 
in connection with this view, a very simple explanation can 
be offered of the presence of an intra-karyosomatic centro- 
some, one which appears to me to render quite unnecessary the 
involved conception of the karyosome discussed above. It 
must be remembered that the premitotic type of division, 
which is the type found where the centrosorne is contained 
within the karyosome, is of a primitive character, as its name 
implies. It is most likely that the reason why the centrosom.e, 
i.e. the intra-nuclear division-centre, is inside the karyosome 
in such cases is simply because the latter body does contain, 
for the time being, the larger proportion, or it may be nearly 
all of the chromatin of the nucleus, the division of which it is 
the function of the centrosorne to bring about and regulate ; 
in other words, because, having regard to the primitive 
character of the mechanism, the function of the division-centre 
is the better performed the more intimately it is associated 
with the chief chromatin-containing constituent of the nucleus. 
Further, on this view a separation of centrosorne and 
karyosome, as the nuclear development reaches a slightly 
more advanced stage, would be readily intelligible. Such an 
occurrence of the division-centre distinct from, or inde- 
pendent of, the karyosome (but at first, of course, remaining 
intra-nuclear) may have been brought about in more than one 
way. Thus it may be the result of a more elaborate develop- 
' It may he noted that Leger and Duhoscq (17), in their adniirahle 
account of the sexual processes among Gregarines, also adopt this 
interpretation of tlie elimination of karyosomatic material. 
