228 Coelomomyces stegomyiae 
forming two to three concentric layers, so closely attached to the organs, that 
in some places it is difficult to separate the tissues of the host from the sur¬ 
rounding mycelium. The latter is also well-developed beneath the hypoderm 
of the host, where it is covered with the pigmented remains of the peripheral 
cells of the fat body (Fig. 5 A). Examined in lactophenol, the fragments of 
mycelium show numerous ramifications, the branches varying from 2 to 6g 
in thickness; while some fragments are more regularly ramified and about 3 /x 
thick (Fig. 3 F), the others are composed of entangled branches with irregular 
thickenings which seem to be formed by a confluence of two or more branches; 
in such places the mycelium attains a width of 5 to 6 /z (Fig. 4 my). 
The main branches of the mycelium are often connected by short transverse 
branches which, in places, show a small diverticulum or a spherical thickening 
(Fig. 3 D and E, x). The mycelium, examined in toto in lactophenol-cotton blue, 
or in stained sections, did not show any transverse walls and is therefore 
unicellular. Its nuclei are very chromatic, crowded in places, and scattered 
elsewhere. Each nucleus is surrounded by a dense layer of protoplasm, which 
in the other parts of the mycelium is filled with vacuoles of various sizes and 
shapes (Fig. 3 A and B). 
III. DEVELOPMENT AND STRUCTURE OF SPORANGIA. 
The majority of the branches show terminal thickenings of various sizes; 
in some branches they are hardly noticeable, while in the others they form a 
pronounced terminal swelling 30 to 35 /z long and 20 to 22 /z thick (Fig. 3 C, sp.). 
The contours of these terminal dilatations are somewhat irregular and their 
surface often shows a series of very fine transverse wrinkles. These thickened 
portions are very difficult to stain in toto , but in sections they show the same 
structure as that of the ordinary mycelium, with the difference that they 
contain a larger number of nuclei, and the protoplasm is more vacuolated 
(Fig. 5 A). At a later stage of development the terminal swellings become 
separated from the mycelium and are found free within the insect’s body-cavity, 
their length varying from 32 to 65 /x. At first they possess a structure identical 
with that of the terminal swelling of the mycelium, but they appear to increase 
in size after becoming free in the host’s perivisceral fluid. The number of their 
nuclei varies with their size. 
At a later stage these bodies become more regularly oval; the peripheral 
layer of protoplasm grows denser (Fig. 5 C) and the external wall thickens 
(Fig. 5 D, w.). The nuclei now increase in number, undergoing several divisions, 
and the protoplasm becomes more dense and basophile. The wall thickens 
progressively and assumes a complicated structure, ending in the development 
of sporangia, the form of the parasite that is most frequently found in the 
perivisceral cavity of the host. The sporangia constitute the main mass of 
parasites which fills the posterior segments of the host (see Fig. 1). When 
removed from the larva the sporangia appear as oval bodies measuring 37-5 
to 57 jj, in length and 20 to 30 /z in width, flattened on one side and convex on 
