52 MICROBES AND TOXINS 



possesses certain characters, inclining one rather to derive it from 

 the flagellates. It too passes through a cycle of development, 

 one stage being in the blood of man, the other in the body of 

 a mosquito of the genus Anopheles. According to the stage 

 of development, the hsematozoa of Laveran have both asexual 

 and sexual reproduction, the latter occurring in the body of 

 the mosquito. 



It cannot be too often insisted on that no protozoon is 

 properly known until all its cycle of development has been 

 investigated and settled. 



Moulds. A slice of bread or a piece of lemon left to 

 itself under suitable conditions of temperature and moisture 

 is soon covered with a fine growth of a whitish or 

 greenish tint ; this is formed by the moulds, lower fungi 

 belonging to the vegetable kingdom. Under the microscope a 

 particle of this growth, teased in a drop of water, shows a 

 felt-work of tubes or filaments, sometimes segmented at 

 intervals, sometimes not ; this felt-work is the mycelium. From 

 the mycelium little stalks stand up vertically bearing a head 

 which itself carries little granules resembling fruit. In the 

 Mucors the head is a spherical sac stuffed full of these 

 granules. In Penicillium the head consists of ramifications 

 or digitations dividing in their turn, the last sections pinching 

 off little pieces, thzconidia; the whole resembles a little brush. 

 In Aspergillus the fructification resembles the flower of an 

 onion. 



A fragment of mycelium put into a suitable medium 

 reproduces the mycelium. The conidia can do the same. 

 In the case of the mucorines two cells can join, fuse, and 

 produce an " egg " ; often these two cells are different, and 

 the reproduction may be regarded as sexual. If mucor is 

 grown at the bottom of a sugary fluid it no longer forms an 

 abundant mycelium ; on the contrary there can be found 

 nothing but short pieces, round or ovoid, which reproduce 

 themselves by budding like yeasts. But any of these pieces 

 put in a sugar-containing medium in contact with the air, 

 forms a mycelium on the surface. This transformation of a 



