COHN, ON EMPUSA MUSC^. 159 



whetlier the tertiary sporidia, when they have reached a wheat- 

 plant, are directly developed into the "smut-fungi" from which 

 are produced the well-known (primary) Til/etia-STpores, and 

 thus close the entire cycle of a complicated alternation of 

 generations. (These results of M. Tidasne's observations 

 have been confirmed by H. Kuhn, of whose merits as an 

 observer Cohn speaks highly, and also by himself) . 



These observations indicate, at any rate, that in the above 

 class of parasitic fungi each spore does not immediately 

 produce a new plant, but in the first place a considerable 

 number of spores of another form and structure, from which 

 only the true mycelium is developed. A very few spores, 

 therefore, are sufficient to produce a vast number of fungi, 

 and in this way to destroy whole ears of corn. 



The author's conclusions respecting the development of 

 the Empusce in the fly were based principally upon the fact, 

 that their origin could in no way be explained according to 

 the views at present prevailing in science, since neither the 

 true spores of i\\e fungus, which are never met with there, 

 could penetrate directly into the abdominal cavity of the 

 diseased animal, nor could any mycelium, in any way origi- 

 nating, form spores which might have germinated upon the 

 surface of the fly. Since, moreover, the youngest conditions 

 of the Empusa, which I have observed, he says, in the fly's 

 blood, were far smaller than and of an entirely difi'erent 

 structure to the characteristic spores, and were also from the 

 first present in vast numbers, the only conclusion left to be 

 drawn Avas that they had arisen in free cell-development, 

 M. Tulasne's discoveries have now, however, at any rate, 

 shown us the possibility of another mode of origin by means 

 of the spores. It might be supposed that in the interior, or 

 on the outer siu'face of a fly, a few, and therefore readily 

 overlooked, Empusa-ST^ores may have become developed, and 

 at first, like the " smut-fungus," may throw out short germ- 

 tubes, which afterwards, in some way, produce a great 

 number of smaller, differently formed cellules {sporidia), 

 which subsequently grow into complete Empusce. In this 

 way, at all events, may be explained the multitudinous ap- 

 pearance of free, minute Empusa-cells, without any necessity 

 for the entrance of as many Empus a -scores, or of a spreading 

 mycelium. 



Although M. Tulasne's researches indicate the possibility 

 of such a mode of development, also, in the genus Empusa, it 

 must be allowed that it has not been proved that such a 

 process really takes place. In opposition to such an assump- 

 tion we have, he says, not only the want of all the supposed 



