MICROSPORIDIA 25 



occupy the lumen of the vessel only, and never take up an intracellular 

 position. The degree of infection is augmented by the multiplication 

 of the parasites by means of fission or budding. Infection is conveyed 

 to fresh hosts by the formation of cnidospores. Bounded parasites, 

 the so-called " sporonts," are found in the terminal portion of the gut 

 as well as in the Malpighian vessels. They contain numerous cnido- 

 spores, with remains of old protoplasm attached. Single spores are 

 found in the faeces. 



When cut into small portions the Malpighian vessels may be 

 prepared as cover-glass specimens. They should be fixed in alcoholic 

 solution of mercuric chloride and stained with iron-hsematoxylin. 

 It will be found quite easy to follow the process by which a single 

 homogeneous nucleus divides twice and produces a fourfold nucleation. 

 The material may also be dried on cover-glasses and stained by 

 Eomanowsky's method ; here the results are more brilliant but less 

 natural. To localize the centre of infection, fix the Malpighian vessels 

 whole, embed, and cut into sections. 



The method of multiplication of P. periplaneta, both by fission 

 and by means of spores, constitutes a true alternation of generation. 

 The phenomenon is observed in other Microsporides, as, for instance, 

 in Thelohania miilleri (L. Pfr.), found in the muscular structure of 

 Gammarus pulex, and T. legeri, Hesse, found in the fat corpuscles 

 of the Anopheles larvae (these forms are extremely small and each 

 sporont contains only eight spores). It is not met with in the same 

 well-defined form, however, in other members of the Neosporidian 

 class. 



An excellent example of a Microsporide of complex development 

 is furnished by Glugea anomala, Mon., a parasite of the stickle-back. 

 These organisms cause cysts, several millimetres in diameter, to appear 

 under the skin, on the gills, and in the ovary. Cover-glass preparations 

 of these cysts, whether fresh or fixed and stained with iron-haema- 

 toxylin, are useful only for the examination of the cnidospores. The 

 latter are furnished with a very long nematocystic thread, which is 

 projected when the specimen is treated with tincture of iodine and 

 left in a damp chamber for twenty-four hours. For further study 

 of the organism the entire cyst should be fixed in alcoholic solution 

 of mercuric chloride and cut into sections. It will then be seen that 

 the cell plasma contains numerous nuclei. In Pleistophora and 

 Thelohania multiplication appears to result from the division of 

 these nuclei, nuclear division being sometimes followed by the division 

 of the entire cell. Within the homogeneous mass of protoplasm, and 

 separated from it by a thin membrane and, in later stages, by a layer 

 of fluid also, uni-nucleate protoplasmic bodies are found which must 

 be regarded as the products of internal budding. These are usually 



