72 Smith .— On Direct Nuclear Divisions in the 
division is further evidence in favour of direct division. It is possible that 
both forms occur, for in Valonia Fairchild ( 1894 ) describes both mitotic and 
amitotic divisions. 
Amitosis has been found in the vegetative mycelia of several of the 
fungi, notably in Penicillium (Gudguen, 1899 ) and the yeasts (Wager, 1898 , 
and Guilliermond, 1903 ). Guilliermond also figured amitosis in Mucor , and 
this compares very favourably with that described above. The nucleus in 
yeast has a very different construction from that in Saprolegnia , and conse¬ 
quently cannot be compared, but the division described for Penicillium 
appears to be very similar to that described in this paper. 
The type of amitosis in Saprolegnia is not a mere fragmentation, but 
it is an ordered division somewhat allied to that described for the nucleus 
of Ancylistes by Dangeard ( 1903 ). This nucleus, however, has a true 
nucleolus which passes out of the membrane as division commences. The 
chromoblast in Saprolegnia has not a true nucleolar function, since it 
takes an active part in the division. 
Summary. 
1. The fungus investigated appears to be a variety of Saprolegnia dioica . 
The vegetative nuclei are typically spherical, but vary in size and shape 
according to the concentration of the cytoplasmic strands and the consequent 
tension exerted by them. 
2 . Only amitotic divisions of the vegetative nuclei have been observed 
during the course of this investigation. 
3. As a rule the nuclei divide between 10 p.m. and 2 a.m., but they can 
at any time be stimulated to division by removing the fungus from very 
cold water to water at 20° to 22° C. 
The writer wishes to express his thanks to Professor O. V. Darbi- 
shire for suggesting the subject of this investigation and giving much 
helpful advice and criticism while it was being carried out. 
Cryptogamic Research Laboratory, 
Department of Botany, University of Bristol, 
July 1922. 
