COHN, ON EMiniSA MUSCJ-:. 155 



were made by Nees v. Esenbeck in 1827, though he did not 

 arrive at any very definite conclusion as to the nature of 

 what he observed. But, in 1835, M. Dumeril declared the 

 fine white dust to be a true mould, which had probably caused 

 the death of the animal, in the same way that plants are 

 killed by different species of Exysiphe. He compares it to 

 the " muscardine" of the silk- worm. 



In 1841, Mr. Berkeley determined the mould observed by 

 Dumeril to be the Bporendonema muscm, Fries., with the 

 following characters : " S. floccis simplicibus in caespitulos 

 sublobatosalbos conglutinatis" ('Systema mycologicum/ 1829, 

 iii, p. 434) ; the fertile filaments (flocci) are said to be filled 

 internally Avith serially disposed, spherical sporidia. 



Cohn, though admitting that the last-mentioned circum- 

 stance may be explained by the action of water upon the 

 contents of the filament, thinks it necessary, in giving a new 

 diagnosis, also to dignify tlie fungus with a new name, and 

 to erect it into a new genus under that of Empusa, with the 

 following characters : " Empusa, entophyta, e tribus constans 

 cellulis, quarrum infima in insecti cujusdam alvo evoluta, 

 mycelii instar tortuosa et ramificata superne prolongatur in 

 mediam, extrorsum tandem erumpentem, stipitis vel basidii 

 instar spora simplici, elastice demum protrusa coronatum." 



Em. musc(£, n. sp. : Cellula myceliiformi ^^^o'" l^^ta, sursum 

 in claviformem -jio'" latam excurrente, spora campanuli- 

 formi = -^y. 



The author gives a long, interesting, and very particular 

 account of his observations upon this parasitic growth, and 

 finally sums up his conclusions in the following propositions, 

 which include all the main points in the paper. 



In a postscript noticing M. Tulasne's observations on the 

 development of the Uredinese,* he himself, however, admits 

 that they are calculated to throw very strong suspicions upon 

 the correctness of one of the main propositions which it 

 seems to have been the object of this memoir to establish, 

 viz., " that in the fluid which fills the abdominal cavity of the 

 diseased fly numerous cells arise by free cell-formation, which 

 cells, by gradual development, are formed into the tricellular 

 Empusa.''' A sort of equivocal generation, the establishment 

 of which in any case will indeed require very much stronger 

 evidence than has yet been afforded, and especially in the in- 

 stance of growths like the present, of whose modes of develop- 

 ment much still remains to be made out. 



* ' Memoire sur les Urediuees et les Ustilaginees.' (Ann. d S n'lf 4 ser 

 t. ii, 1854, pp. 77—193.) ' '' ' ' ' 



