INSECT FUNGI 191 
tion occurs only when hyphae of the two kinds come into 
contact (heterothallic forms). . 
287. The Insect-fungi (Entomophthoraceae) are well 
represented by the Fly-fungus (Entomophthora muscae), 
which in the autumn is destructive to house-flies. It 
consists of small tubular coenocytes which grow in the 
moist tissues of the fly, and at last pierce the 
skin, producing minute terminal spores, which 
give the fly a powdery appearance. These 
spores (called, also, conidia) may be seen as a 
whitish halo surrounding the spot to which the “% 
fly (now dead) has attached itself. Round yg si— 
and thick-walled resting spores (formed by }2tomoph- 
the union of gametes similar to those of Black 
Molds) have been observed in some species, and may be 
studied in the Grasshopper Fungus (Entomophthora 
grylli), which destroys great numbers of grasshoppers 
every autumn. 
The Sexual Organs of the Water Molds, Downy Mil- 
dews, Black Molds, and Insect Fungi show a progressive 
degeneration from the typical structure occurring in the 
Green Felts. In the Water Molds there is a suppression 
of the sperms, the antherid protoplasm being transferred 
directly to the egg. This is continued with little change 
throughout the Downy Mildews and White Rusts, which 
being non-aquatic could scarcely make use of motile 
sperms. The sexual organs of the Black Molds are 
apparently of the same general type as those of Water 
Molds and Downy Mildews, each being an end cell cut 
off from a reproductive filament, but in Black Molds 
these filaments show little differentiation. They unite 
prematurely, before the oogone has developed an egg, 
and before the other filament has developed its anther- 
idial protoplasm. They are physically under-developed 
