Chapter V. 



Fungi. Parasites on Animals. 



An account of the parasitic fungi would be incomplete with- 

 out some mention of those fungi which attack animals and 

 cause disease in them. These fungi are becoming more and 

 more of economic importance, especially in their use in com- 

 bating insect invasions on agricultural crops. They are fur- 

 thermore of great interest in the diseases which they cause in 

 man and the lower animals. In general, these fungus parasites 

 belong to the lower or algal fungi, the water molds, bread- 

 mold-allies and insect molds; but not a few are found amongst 

 the higher fungi, e. g., the caterpillar fungus, the green mold, 

 and even yeast-like fungi. 



Diseases of lower animals. Not even the most lowly 

 groups of animals are exempt from fungus parasites on the 

 contrary, they seem to suffer to an unjust degree. Those 

 small unicellular animals which usually inhabit the water are 

 often attacked by the simplest of fungi, also unicellular and very 

 minute plants. The fungus finds its way through the wall of 

 the animal cell and draws its nourishment from the animal 

 protoplasm. Sometimes the fungus is exceedingly minute 

 and may confine itself to only a special port'on of the proto- 

 plasm, as do nuclear parasites. 



Where (as in the Coelenterates) the host animal possesses 

 a protective coat of lime the invading parasite may bore 

 through the lime. The resting stage of these small animal- 

 cules furnishes an especially inviting host, since here the fun- 

 gus meets with less resistance. One parasitic fungus is known 

 to live only on the eggs of the little animals known as wheel ani- 

 malcules. 



The pin worms are likewise subject to fungus diseases and 

 one often finds an epidemic raging amongst colonies of 

 these little creatures. As these worms are often greenhouse 



