468 Harper. — Cell-Division in Sporangia and Asci. 
the relations of the nuclei to the formation of the cilia. 
As to the actual method of cell-division whereby the proto- 
plasm of the sporangium is cut up into the swarm-spores, the 
earlier observers seem to have been too much influenced 
by theories of cell-formation in general. A brief summary 
of the views of Nageli, Unger, Schleiden, Meyen and others, 
is given by Pringsheim 1 in the introduction to his account 
of the development of Achlya prolifer a. Biisgen 2 also 
reviews briefly the views of the older authors as to the nature 
of the spore-formation and its bearing on cell theories. 
Unger held that the sporangium was formed simply by 
the building of the basal septum, and was an example of 
simple meristematic cell-formation. 
Nageli interpreted the same phenomena of sporangium- 
formation as indicating the building of a complete new cell 
in the end of the hypha with a new wall just inside the 
sporangium wall. It was for him a case of ‘ wandstandige 
Zellbildung/ and was used to still further support the 
doctrine that all new cells arise in old ones by free cell- 
formation. Nageli further believed, in agreement with the 
views of Schleiden, that the individualizing of the spores 
was due to preceding formation of cytoblasts (nuclei), centres 
around which the cell is differentiated. According to 
Pringsheim’s own account of the process in Achlya prolifera 
{Saprolegnia ferax , Ktz.) the septum which cuts off the 
sporangium is a double membrane running up on the spo- 
rangium wall and down on the wall of the hypha for a short 
distance, thus forming in optical section three-cornered 
intercellular spaces. The septum becomes convex downward. 
A lumen now appears in the sporangium due to influx of 
water (areola of Unger). 
The spores appear first as prominences pushing into the 
sporangium-lumen. No boundary line about them is visible. 
1 Die Entwicklungsgeschichte der Achlya prolifera, Nov. Act. Acad. Caes. Leop. 
Carol. Nat. Cur., vol. xxiii, p. i, 1850. 
2 Die Entvvicklung der Phycomycetensporangien. Jahrbticher fiir Wiss. Bot., 
Bd. xiii, 1882. 
