5 1 8 Harper. — Cell- Division in Sporangia and Asci. 
while remaining one celled. My earlier studies of ascospores 
led me to the erroneous conclusion that the one-celled 
ascospore was regularly uninucleate. I have since found 
ascospores in which nuclear division had occurred without 
cell division, and such cases have also been pointed out by 
other investigators \ These cases are interesting because of 
the possibility of a reduction of the number of chromosomes 
at this stage, and should be investigated further as to the 
phenomena of nuclear division. 
That in Synchitrinm the embryonic growth in the spo- 
rangium produces sporangia, while in Pilobolus and in all asci 
with multicellular spores the germination is by a germ-tube 
from each spore-cell, may be, as has been suggested for other 
similar cases, entirely a matter of adaptation in the one case 
to germination in water, and in the other to germination in 
air or solid media. The aim of the process is always to 
produce a larger number of reproductive bodies, and thus 
to use up advantageously any excess of nutritive materials 
accumulated in the sporangium or ascus. In the Exoasci 
an analogous embryonic growth takes the form of yeast-like 
budding, and the number of conidia produced is plainly 
dependent on the amount of nutriment available in the ascus. 
A possible comparison might be made between the uni- 
nucleate stage of Synchitrinm and the uninucleate stage of the 
ascus. Each is followed by a multinucleated stage and 
cleavage to form uninucleate spores, but the comparison is 
an artificial one. The divisions in Synchitrinm , though they 
lead directly to spore-formation, are probably morphologically 
equivalent to the nuclear divisions that take place in the 
mycelium and bulb of Pilobolus. At any rate, some possible 
connecting types should be found to give the comparison 
any value. 
As the mechanism which effects the division of the mother 
cell into daughter cells, we have in the ascus the kinoplasmic 
fibres, and in the sporangium constriction-furrows from the 
Dittrich, Zur Entwicklungsgeschichte der Helvellineen, Beitrage zur Biol, der 
Pflanze, 1899. 
