682 McAllister Nuclear Division in Tetraspora lubrica. 
In Acanthocystis , according to Schaudinn (12), the centrosphere lies in 
the cytoplasm. It divides and its halves separate, moving to the poles of 
the nucleus. There seems little essential difference between the mitosis 
here and that in the other animal mitoses, in winch asters are involved. In 
Paramoeba , according to the same author, the only important difference 
lies in the difference in the size of the centrospheres ‘ Nebenkorper’, which 
are nearly as large as the nucleus. Wilson (54) says : ‘ Paramoeba appears 
to differ from Euglena mainly in the fact that at the close of division the 
sphere is in the former left outside the daughter nucleus, and in the latter 
enclosed within it.’ There seems, however, a greater difference than this, 
for in Euglena no spindle is described or figured, while in the case of 
P ar amoeba a very definite spindle figure is reported, with the large centro- 
spheres at the poles. 
In the light of these divergent types of nuclear division in the Protozoa, 
mitosis in the Protophytes, and especially in those forms regarded as most 
closely related to the Protozoans, is of especial interest. Thus far no results 
have been obtained in any of the green plants which seem in any way to 
correspond with the results reported by investigators on the Protozoa.- 
Mitosis in Spirogyra has been the subject of numerous investigations — 
probably more than in all other Algae combined — but very great variations 
exist in the accounts of mitosis in this Alga, and the discrepancies are so 
marked as to arouse the suspicion that the described appearances cannot all 
be normal. If we accept the reported accounts of mitosis in Spirogyra as 
accurate, we have in this genus greater and more fundamental variations in 
the phenomena of nuclear division than have been reported in all the 
remaining green plants from the Algae to the Angiosperms. The chromo- 
somes have been reported as arising entirely from the nucleole (33, 34, 2) 
or partly from the nucleole and partly from the reticulum (15, 16, 56), or 
entirely from the reticulum (50, 46). Lutman’s work on Closterium (31) 
seems to prove clearly that in this Conjugate nuclear division follows the 
well-known steps established for the higher plants. Van Wisselingh (57), 
working independently, came to the same conclusions at about the same 
time. 
In view of the great similarity in the most conspicuous and constant 
characteristics in the nuclear division in all the green plants outside of 
Spirogyra and the other investigated Conjugatae, Moll’s (36) suggestion 
that we should not expect the same mitotic phenomena in all species of 
Spirogyra must be regarded as based upon an unstable foundation. 
The literature on the mitosis' in Spirogyra has been recently fully 
reviewed by Berghs (2), Lutman (31), and others, so that a detailed review 
here seems superfluous. 
Strasburger’s earlier work on Cladophora (45) has recently been sub- 
stantiated and extended by Nemec (37). According to these accounts, the 
