318 THE MICROSCOPE AND ITb REVELATIONS. 



occasioning the destruction of this tissue, which is very important as a 

 reservoir of nutriment to the animal when it is about to pass into its 

 chrysalis condition. The disease invariably occasions the death of the 

 worm which it attacks; but it seldom shows itself externally until after- 

 wards, when it rapidly shoots-forth from beneath the skin, especially at the 

 junction of the rings of the body. Although it spontaneously attacks 

 only the larva, yet it may be communicated by inoculation to the chry- 

 salis and the moth, as well as to the worm; and it has also been observed 

 to attack other Lepidopterous Insects. A careful investigation of the 

 circumstances which favor the development of this disease was made by 

 Audouin, who first discovered its real nature; and he showed that its 

 spread was favored by the overcrowding of the worms in the breeding 

 establishments, and particularly by the practice of throwing the bodies 

 of such as died into a heap into the immediate neighborhood of the living 

 worms: for this heap speedily became covered with this kind of ' mould,' 

 which found upon it a most congenial soil; and it kept up a continual 

 supply of sporules, which, being diffused through the atmosphere of the 

 neighborhood, were drawn into the breathing pores of individuals previ- 

 ously healthy. The precautions obviously suggested by the knowledge 

 of the nature of the disease, thus afforded by the Microscope, having 

 been duly put in force, its extension was successfully kept down. 



314. An^example of the like kind is frequently presented in the 

 destruction of the common House-fly by a minute fungus termed Em- 

 pusa muscce. In. its fully developed condition, the spore-bearing filaments 

 of this plant stand out from the body of the fly like the ' pile ' of velvet; 

 and the spores thrown off from these in all directions forma white circle 

 round it, as it rests motionless on a window-pane. The filaments which 

 show themselves externally are the fructification of the fungus which 

 occupies the interior of the Fly's body; and this originates in minute 

 corpuscles which find their way into the circulating fluid from without. 

 A healthy fly shut up with a diseased one, takes the disease from it by 

 the deposit of a sporule on some part of its surface; for this, beginning 

 to germinate, sends out a process which finds its way into the interior, 

 either through the breathing-pores, or between the rings of the body; 

 and having reached the interior cavity, it gives off the minute corpuscles 

 which constitute the earliest stage of the Empusa. Again it is not all 

 uncommon in the West Indies, to see individuals of a species of Polistes 

 (the representative of the Wasp of our own country) flying about with 

 plants of their own length projecting from some part of their surface, the 

 germs of which have been probably introduced (as in the preceding case) 

 through the breathing-pores at their sides, and have taken root in their 

 substance, so as to produce a luxuriant vegetation. In time, however, 

 this fungous growth spreads through the body, and destroys the life of 

 the insect; it then seems to grow more rapidly, the decomposing tissue 

 of the dead body being still more adapted than the living structure to 

 afford it nutriment. A similar growth of different species of the genus- 

 Splicer ia takes place in the bodies of certain caterpillars, in New Zealand, 

 Australia, and China; and being thus completely pervaded by a dense 

 substance, which, when dried, has almost the solidity of wood, these 

 caterpillars come to present the appearance of twigs, with long slender 

 stalks that are formed by the growth of the fungus itseF. The Chinese- 

 species is valued as a medicinal drug. 



315. The stomachs and intestines of many Worms and Insects are 

 infested with parasiticFungi, which grow there with great luxuriance. In 



