XOTES ON SPOROZOA III. 
209 
inent of the lueclianisra of division ; an example of this is 
seen in the case of Spongomonas, to which reference 
has previously been made, where the centrosome passes out 
of tlie karyosome at the period of division and a definite 
mitotic figure is formed. Or, on the other hand, it may be 
due to the development of another type of nuclear structure, 
where, either during certain phases in the life-history or 
throughout the Avhole cycle, there is no longer a karyosome 
present in the nucleus as such, but the chromatin is more or 
less uniformly distributed on a reticulum throughout the 
general nuclear substance, in the middle of which the 
centrosome may persist.' And it is in this direction that tlie 
nuclear constitution has apparently developed in the Haemo- 
gregarines. Lastly, a further stage in nuclear evolution 
would be reached by a combination of the two lines of 
development indicated, i. e. by the elaboration of the nuclear 
structure itself, associated with a more perfect development 
of tlie division-mechanism ; and thus a condition might be 
arrived at such as is seen in the danghter-nuclei formed 
during the period of nuclear multiplication, whicli precedes 
gamete-formation, in many (Iregarines (cf. the figures of 
Brasil [4J, Leger and Duboscq [loc. cit.], Woodcock [39]), 
wliere we find perhaps tlie highest grade of nuclear 
constitution and mode of division attained among the 
Sporozoa. 
‘ It is important to note that even where a division-centre is certainly 
pi-esent during particular phases of a life-cycle, this may nevertheless 
be wanting, or at any rate not recognisable, during other periods of the 
same life-cycle. Thus, in many Coccidia (e.g. Coccidium schu- 
hergi, Cyclospora karyolytica, according to Schaudinn), the 
division of the definitive nucleus of the zygote to form the sporoblast- 
nuclei is direct; hut, on the other hand, in Ad e lea (cf. A. ovata, 
mesnili [Perez, 25] and hartmanni) the sporogonic divisions appear 
to be promitotic, i. e. more or less compai-able to the schizogonic ones, 
allowance being made for the absence of a karyosome). Again, in the 
nuclear divisions of the sporont of the Gregarine, Diplodina irregu- 
laris, I have shown (39) that the first ones are direct (amitotic), the 
later ones mitotic. 
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