230 Coelomomyces stegomyiae 
the other (Fig. 6 A). The wall of the sporangium when highly magnified shows a 
very fine granular structure and many small clear lenticular spots (Fig. 6 B,a .); 
the convex side shows a very fine line running from pole to pole. 
Sections of the sporangium show that the wall consists of two distinct 
layers: (1) an internal, thin, structureless layer, 0-7/x thick (Fig. 7 A, en.), and 
(2) an external layer (Fig. 7 A, ex.) 1*7 to 2 /x thick, of a yellowish colour, and 
showing numerous apertures (a.) already referred to as clear spots on the surface 
of the sporangium. By pressing a sporangium in a drop of water between the 
slide and a coverglass a number of small oily drops are seen to escape from 
the apertures of the external wall. 
IV. DEVELOPMENT AND STRUCTURE OF SPORES. 
The young sporangium is filled with very dense and basophile protoplasm, 
containing a great number of small nuclei (Fig. 7 B). As the sporangium 
Fig. 6. Coelomomyces stegomyiae. A, a completely formed sporangium showing the clear line, upon 
its convex side; B, sporangium showing the distribution of small apertures, a., upon its 
external wall; C, breaking up of a sporangium under pressure. 
develops the protoplasm divides into many portions, each of which surrounds 
a nucleus (Fig. 7 C) and gives rise to as many small spherical cells as there were 
nuclei (Fig. 7 D). These cells, 3 /x in diameter, become elongated, with a more 
or less central nucleus (Fig. 7 E and F). The sporangia filled with these lozenge¬ 
shaped spores, 5 fi long and 1 /x in diameter, were not very numerous, and they 
represent the last stage of the parasite which I could find in the host. Un¬ 
fortunately the available material was insufficient for a more detailed study of 
these spores. Their shape, however, and the fact that they probably represent 
the final infective stage of a parasite of an aquatic host suggest that these 
spores are provided with one or two flagella and are the actual flagellispores or 
zoospores which are so characteristic of some groups of lower fungi; this 
supposition could be readily demonstrated by an examination of living 
material. 
