270 Trow . — Observations on the Biology and 
observations are practically confirmatory of those already 
made by De Bary. Although the microscope has been con- 
siderably improved during the last twenty years it is only 
just to say that the most recent observations on living material 
add little to the knowledge handed down to us by the older 
observers. 
The only observations of importance on the karyology of 
Pythium , founded on the examination of fixed and stained 
material, are those of Fisch (’85) and Dangeard ( 5 92). 
Fisch states: ‘ Im jungen Oogonium, vor der Oospharen- 
bildung, sind ziemlich regelmassig 10-20 Zellkerne anzutreffen. 
Bei der Bildung der Oosphare riicken sie zusammen, bis sie 
dicht aneinander liegen, und verschmelzen dann zu einem 
einzigen ziemlich grossen Eikern. In der Antheridialzelle 
habe ich immer nur einen Zellkern gefunden, bezweifle aber 
nicht, dass auch mehrere vorkommen konnen, die aber dann 
sicher vor der Befruchtung zu einem einzigen verschmelzen. 
Der Zellkern der Antheridialzelle wandert mit dem Gono- 
plasma in die Oosphare liber und verschwindet hier mit dem 
Eikern/ At the time Fisch wrote this it appears to have been 
quite the fashion to assume that a multinucleate organ became 
uninucleate by a process of wholesale nuclear fusions. The 
process of fusion was often definitely described, as by Fisch 
in the case before us. Careful observations have, however, 
shown that in many cases at least, e. g. Vaucheria , Perono- 
spora , Cystopus , Saprolegnia , and Achlya , no such fusions are 
demonstrable, and that the uninucleate condition is reached 
in quite a different fashion. It is not difficult for the 
experienced botanist to realize how such errors of interpre- 
tation can arise. Even with the most refined of the modern 
methods it is often difficult to get thoroughly satisfactory 
proofs of the behaviour of the nuclei in any one case. 
Wager (’00) has indeed felt himself in a position to question 
the tenability of Fisch’s view. He says, ‘ It is probable that 
the mode of fertilization described by Fisch for Pythium will 
be found to be untenable/ His view is a just one, but it is as 
well to bear in mind that great differences in the karyology 
