21 
of the process of vacuolation for homologising the different 
stadia in the development of atypical sacs. The process just 
described and well-known to all students of morphology, gives 
cause to call the attention to the following points: 
1°. Polarisation (vacuolation) is a function of the embryosac (de- 
veloping megaspore). It does not accompany the megaspore- 
formation, but its development. It commences as soon as megaspore 
development begins. 
This remarkably constant character, viz. vacuolation just pre- 
ceding the first division of the functioning megaspore, furnishes 
us with a new characteristic by which megaspores may be 
recognised, even when the “row of fouré is not formed. As long 
as plasm remains homogenous, megaspore formation is still 
going on. As soon as vacuolation commences, megaspore deve- 
lopment has begun. So the nuclei just preceding vacuolation are 
to be considered as megaspore nuclei. 
I am well aware that this proposed use of vacuolation as 
means of recognising megaspores is nothing more than a working 
hypothesis. Its progress in the normal sac is no reason in itselt 
to assume that vacuolation always and under all circumstances 
should be bound to the early stages of spore-germination. There- 
fore I will move some arguments in favour of the hypothesis. 
Firstly in literature no case is met with in which vacuolation 
did not commence just after megaspore-formation. 
Secondly the hypothesis is confirmed by all well-established 
and undoubtable cases of megaspore-formation under abnormal 
conditions (which fully justifies the application of the idea to 
those cases in which homologising meets with difficulties). For 
instance: Smrra (1911) describes the embryosac-mothercell-nucleus 
of Clintonia giving rise to a row of four nuclei, not separated 
by cell walls. Three of these soon desintegrate, only the upper 
one developing. Nobody will dispute the megaspore-character of 
these four nuclei. Though all four megaspores are lying 2 the 
same cell, plasm remains homogenous up to the first division of 
the developing nucleus. According to Jounson (1914) the walls 
between the megaspores in Peperomia hispidula are very deli- 
cate and soon disappear, leaving four nuclei in a continuous 
