[Illustration: FIG. 85.--_Empusa muscæ_ (Fly-mould). I. A fly killed by the fungus, surrounded by a white layer of conidia. II. The conidiophores (_t_) projecting from the body of the fly. Some of the conidia, a few of which have developed secondary conidia, are attached to the hairs (mag. 80 times). III. A perfect hypha. IV. A hypha in the act of ejecting a conidium (_c_), enveloped in a sticky slime (_g_). V. A conidium which has developed a secondary conidium (_sc_). VI. A branched hypha produced by cultivation. VII. A secondary conidium which has produced a small mycelium (_m_). VIII. A conidium germinating on the fly’s body. IX. Mycelium. X. Conidia germinating like yeast in the fatty tissue of the fly. (III.-VII. and IX. magnified 300 times; VIII. and X. magnified 500 times.)] A fertilisation, a passage of the contents of the antheridium to the egg-cell, has as yet only been observed in _Pythium_; in _Phytophthora_ only one small mass of protoplasm passes through the fertilising tube to the egg-cell; in _Peronospora_ and the Saprolegniaceæ no protoplasm can be observed to pass through the fertilising tube, so that in these instances _parthenogenesis_ takes place; _Saprolegnia thuretii_, etc., have generally even no antheridia, but nevertheless form normal oospores. Fertilisation of the egg-cell by means of self-motile _spermatozoids_ is only found in _Monoblepharis sphærica_. =A.= Asexual reproduction by conidia only. Family 1. =Entomophthorales.= The mycelium is richly branched. The family is a transitional step to the conidia-bearing Zygomycetes, since the oospores of many members of this family arise, and are formed, like zygospores. Order 1. =Entomophthoraceæ.= Mycelium abundantly developed. This most frequently lives parasitically in living insects, causing their death. The conidiophores forming the conidial-layer project from the skin, and abstrict a proportionately large conidium which is ejected with considerable force, and by this means transferred to other insects. These become infected by the entrance of the germ-tube into their bodies. The spherical, brown resting-spores develope inside the bodies of insects and germinate by emitting a germ-tube.