Harper. — Cell- Division in Sporangia and Aset. 479 
divides into at least four daughter nuclei. Gradually the 
granules between the spores are absorbed, and the latter are 
separated only by an oil-like Zwischensubstanz. The spores 
are then pressed out by the growth upward of a new 
sporangium from below. These processes were studied by 
the author on living material and on sporangia stained and 
studied in toto : and I can but believe that the process would 
show more resemblance to that in Pilobolus if studied on 
abundance of material in all stages and prepared in serial 
sections. The appearance of the angular vacuoles may well 
be a stage in the cleavage process, and their disappearance 
later may be due to the swelling of the already separated 
spores, whereby they are so closely pressed together that their 
boundary lines are invisible except in thin and differentially 
stained sections. It is to be remembered that Biisgen 
similarly was convinced by a study of the living material that 
the spores of the Saprolegnieae are formed completely only 
to immediately fuse once more into a homogeneous mass 
which is later cut up a second time into the definitive spore- 
bodies. It is doubtless the case in Saprolegnia that this 
apparent fusion after the spores have been once cut out is 
merely due to the swelling, whereby they become so closely 
pressed together that the plasma-membranes bounding each 
are indistinguishable without special preparation. If it could 
be assumed that the formation of angular vacuoles brings 
about the separation of the protoplasm into spores in Ascoidea 
the process would agree with what I have described below 
for a number of sporangia. If, however, the definitive cleavage 
is brought about by aggregation of hyaline plasma about the 
nuclei as centres, these hyaline masses becoming in some 
unknown fashion surrounded by a wall, the process is so far 
unique, and its homologies must be sought in some forms 
other than the asci or sporangia which have yet been 
studied. 
In Protomyces Bellidis , according to Popta, the contents of 
the sporangium become differentiated into a wall-layer and 
a central vacuole. The wall-layer is divided then simul- 
