OXNERELLA MA ULTIMA. 
533 
the centroplast appears to divide before the nucleus, and to 
take up the position of a centrosome during the division of 
the latter, it is a curious fact — assuming the account to be 
correct — that the nuclear division itself is apparently a kind 
of amitosis. These observations do not furnish a very sub- 
stantial confirmation, therefore, of Schaudinn’s statement that 
the centroplast plays the part of a centrosome in the mitosis 
of the heliozoan nucleus. 
It has long seemed to me desirable that the behaviour of 
the centroplast during the division of those Heliozoa possessing 
this organ should be carefully studied and described. As 
experience has shown, Schaudinn’s brief statements and 
incomplete descriptions are not always to be accepted as 
established facts ; for the magnitude of his mistakes is 
beginning already to rival that of his successes. 
It is for this reason that I have described the division of 
Oxnerella in some detail. My own observations induce me 
to believe that Scliaudimfis account of the division of Acan- 
thocystis is almost certainly correct; and it therefore 
appears to me justifiable to conclude that the centroplast 
actually does behave during nuclear division, in those 
Heliozoa which possess a single nucleus, precisely 
like the centrosome in a typical mitosis in a metazoan cell. 
We have still to learn, however, the part (if any) played by 
the centroplast in the division of those Heliozoa which are 
multinucleate. 
Although I follow Schaudinn up to a certain point — as just 
noted — I am unable to concur in his speculations. On the 
evidence of the observations just considered, but more 
especially from his observations on the origin of the centro- 
methods of nuclear division in which a “ centriole ” is said to be 
present, and later to become the centroplast of a new individual. 
Although this is several times stated to occur, I can find no direct 
evidence in support of the statement, which appears to be merely an 
assumption based upon Schaudinn’s statements about Acantho- 
cystis. Accordingly, I do not think Zuelzer’s assertions can be 
regarded as confirmations of Schaudinn’s results. 
