Harper . — Cell-Division in Sporangia and As ci. 491 
widely distributed, commonest, and in some cases such as 
Pilobolus one of the most highly perfected methods of 
asexual reproduction and spore distribution known among 
the Fungi. 
Brefeld 1 has given very full accounts of the external 
anatomy of Pilobolus and has also described the behaviour 
of very numerous forms under cultivation with varying 
conditions of temperature, &c. He has not especially investi- 
gated the phenomena of spore-formation. He attempts 
however to maintain and strengthen the doctrine that the 
mucilaginous jelly in which the spores *of many Muco- 
rineae are imbedded is identical with the epiplasm of the 
ascus. 
The study of these forms of the Zygomycetes, apart from 
their interest as illustrating the mechanics of protoplasmic 
division in coenocytes, has gained a certain further importance 
since, as is known, the doctrine has been advanced by Brefeld 
that they illustrate in their vegetative sporangia the ancestral 
types in the development of the ascus which is, according 
to this view, only a sporangium which has become definite 
in its size, form, and in the number of spores which it pro- 
duces. Evidence for or against this doctrine can perhaps be 
obtained by an exact and complete study of the processes 
in the two structures, and I hope to contribute something 
to this end in the following account. 
I have investigated especially the phenomena in the 
sporangium of Pilobolus , and have used the common species 
P. crystallinus , from which all the figures illustrating spore- 
formation are made. I have, however, confirmed the principal 
points in the process by studies on P. oedipus and P. micro - 
sporus. Pilobolus is very readily cultivated in the manner 
described by Brefeld. The fungus always appears on horse- 
dung left for a few days under a bell jar, but to get an 
abundance of material at the proper stage of development 
it is better to resort to the simple culture methods described 
by Brefeld. These consist simply in infecting a mass of dung, 
1 Botanische Unters. iib. Schimmelpilze, i. Heft, 1872. 
