ZYGOMYCETES 343 



of the host, the surrounding mycele disappearing. On germination, 

 which Nowakowski describes in Empusa Grylli (Fres.), a short pro- 

 mycele is emitted which bears a single spore. 



Commonly, however, neither zygosperms nor azygosperms are 

 formed, and after the death of the insect, spores are produced on its 

 outer surface. In the case of Empusa — for example, E. Muscas (Cohn), 

 which attacks the common house-fly in large numbers in autumn— the 

 yeast-like mycelial cells, at the time of the death of the insect, send 

 forth each a tube, which bursts through the skin, and outside becomes 

 a short club-shaped sporophore bearing a single acrospore. Each 

 sporophore bears but one spore, and then perishes. The spores are 

 capable of germination at once, but the power lasts only for a few days. 

 Affected flies in this condition are common enough objects attached to 

 windows, &c., and surrounded by a whitish mass of spores. The 

 mycele of Entomophthora, which is septate, much branched, and often 

 anastomosing, sends branches through the skin to the outer surface, 

 where farther ramification takes place, investing the body of the insect. 

 These branches range themselves at right angles to the insect's body, 

 and terminate together at nearly the same elevation. Each such branch 

 is a sporophore, which, as in Empusa, forms a single acrospore. The 

 spores are capable of germination at once like those of Empusa ; and in 

 both genera either a very short tube is formed, bearing a secondary 

 spore, as in the promycele of the zygosperm, which, on germination, may 

 attack a fresh insect, or the germ-tube of the primary spore may do so 

 without the intervention of secondary spores. 



Completoria complens (Lohde), found by Leitgeb in fern prothallia, 

 and Conidiobolus utriculosus (Bref ), described by Brefeld as a parasite 

 on Tremellini, are two forms placed here which, unlike the rest of the 

 group, do not attack insects. Brefeld, who has investigated the group 

 minutely, does not accept the conjugation as a real one, and brings 

 forward arguments against it based on the anastomosing of hyphas and 

 the situation of the zygosperms. His opinion, if accepted, would lead 

 to placing the group elsewhere ; but de Bary states (' Comparative 

 Morph.,' p. 159) that Nowakowski's and Brefeld's different observations 

 may be explained by the different behaviour of different species. 



Literature. 



gfefeid Untersuch. iiber die Entwickel. der Empusa Muscae und Empusa radicans 



und die durch sie verursachten Epidemien der Stubenfliegen und Raupen 

 (Abhandl. d. Naturforsch. Gesellsch. zu Halle, xii.). 



Brefeld— Ueber Entomophthoreen und ihre Verwandten (Sitzungsber. d. Gesellsch. 

 Naturforsc'i. Freunde zu Berlin, 1877). See also Bot. Zeit., 1877, p. 345. 



gi-efeld— Bot. Unters. iiber Schimmelpilze (Ent. radicans), iv., 1881, p. 97. 



