150 COMPARATIVE ANATOMY 



streaming movements last longest in the direction in which 

 locomotion is taking place. It is easy to observe that this 

 slimy sheet of protoplasm, the plasmodium, is irritable, selective 

 and assimilative. If the surface on which it crawls becomes 

 too dry it will move off to a wetter portion of it. If exposed 

 to a bright light it will move off to any shaded corner which 

 is available ; unless, indeed, it is about to form spores, when it 

 will move out of the shade and seek the light; and under 

 the same circumstances it will leave a damp for a drier situa- 

 tion. Still more characteristic are its movements in search of 

 food. If a plasmodium is creeping along one edge of some 

 moist surface a sheet of wet blotting paper or a piece of wood 

 and a piece of its food fungus, Stereum, be placed at the opposite 

 edge, the whole plasmodium will move off towards it, flow over 

 it, and engulph it. Small pieces of the fungus or individual 

 hyphse are soon seen to be ingested, and each ingested piece 

 is enclosed in a food-vacuole which is probably secreted round 

 it, just as in Amoeba. The protoplasmic contents of the 

 hyphse are digested and assimilated, the indigestible remains 

 being expelled much in the same way as in Amoeba. These 

 movements in search of moisture, shade, or food are so slow as 

 to be imperceptible ; but if a plasmodium, with a piece of its 

 food-fungus placed a few inches away from it, be left for a 

 while, it will be found, after a few hours, to have advanced up 

 to its prey, and to be surrounding it. A plasmodium may be 

 killed in osmic acid, or any other of the ordinary killing and fix- 

 ing reagents, and stained for examination of the nuclei. These 

 are very numerous, and they continue to multiply, as long as 

 the plasmodium is active and well fed, by mitotic division. In 

 mitosis a spindle of achromatic fibres is formed, the chromatin 

 is gathered at the equator of the spindle in the form of a 

 number of chromosomes, which divide, and their products pass 

 to opposite poles of the spindle in the usual manner. There 

 is some evidence that in an actively-moving arid streaming 

 plasmodium the nuclei also multiply amitotically, but actual 

 division of the nucleus without mitosis has not been seen. 

 The reproduction of Badhamia is so similar to that of some 

 of the lowest forms of plants, that it and its allies are described 

 in botanical works as plants. When reproduction is about to 

 take place, the plasmodium emerges from under the bark or 

 crevice of wood in which it may be hidden, and seeks the 



