CHAPTER IX. — MODE OF LIFE OF THE MYCETOZOA. 45 I 



Further investigation is necessary to determine whether other causes also may 

 not assist in certain cases to give rise to the latter phenomenon ; the question also, 

 whether the peculiar characters of plasmodia under discussion may not change at a 

 certain period of their development in relation to other things, as well as to 

 hydrotropism, has still to be examined, especially with reference to a statement 

 of Hofmeister a that certain plasmodia moved towards the side of strongest 

 illumination. 



To the movements which have now been described must be added one more 

 which requires a brief consideration. It was stated above on page 425 that small 

 solid bodies are engulphed in the substance of the plasmodia, at least in the Cal- 

 careae or Physareae. This is effected by definite movements; the surface of 

 the plasmodium rises cushion-like round the bodies which are in contact with it, 

 and the margins of the raised part gradually run together over them and cover 

 them. 



This phenomenon occurs in the plasmodia, as soon as they have been formed by 

 coalescence of swarm-cells, but not in the swarm-cells themselves, if we put aside 

 certain isolated observations on Dictyostelium which have yet to be confirmed. It is 

 not confined to any particular spot of the plasmodium, and may continue till 

 sporangia begin to be formed ; then the foreign bodies which have been absorbed 

 and are still present are all ejected, some of them even at an earlier period. All this 

 shows, that the solid bodies are not simply squeezed into the soft and passive 

 substance of the plasmodium, but that there is a reaction of the plasmodium 

 in response to the stimulus which it experiences from contact with them. 



Substances of various kinds are taken in this way into the substance of the 

 plasmodium : fragments of dead vegetable cells, spores of Fungi and of the 

 Myxomycetes themselves, sclerotium-cells of Myxomycetes, grains of starch, small 

 portions of colouring matters if brought near the plasmodium. 



All these substances it should be observed consist of organic compounds, and it 

 is highly probable that some of them at least supply food to the plasmodium which 

 has engulphed them. It is not certainly ascertained whether entirely indifferent 

 inorganic substances are absorbed by it. The question therefore remains 

 unanswered, whether the movements of engulphing are caused by the purely 

 mechanical stimulus of contact, or by certain chemical qualities of the substance to be 

 engulphed. In the latter case the phenomenon would rank immediately with the 

 movement in the direction of nutrient bodies described above, and both would be 

 special cases of a more general law of reaction in response to chemical irritants. An 

 old observation of my own supports the view that the reaction not only is or may be 

 dependent on a definite chemical quality in the body which causes the stimulus, but 

 that plasmodia of different kinds react unequally on the same stimulation. A number 

 of pieces of carmine were absorbed by Didymium Serpula, scarcely any by Chondrio- 

 derma difforme. 



Section CXXVIII. The process of nutrition takes place only in the 

 amoeboid states of the Mycetozoa, in the swarm-cells therefore and the plasmodia. 

 All the better known Myxomycetes in their actual primary adaptation are saprophytes ; 



1 Pflanzenzelle, p. 20. 



G g 2 



