Journal of 



y< 



Applied Microscopy. 



Volume I, 



FEBRUARY, 1898. 



Number 2 



Methods of Study of the Myxamoebae and the Plasmodia 



of the Mycetozoa. 



HOWARD AYERS, Ph. D. 

 Professor of Biology, University of Missouri. 



GEOTROPIC, HELEOTROPIC, CHEMOTROPIC, 

 THERMOTROPIC, MECHANICAL AND ELEC- 

 TRICAL STIMULI, AND THE EFFECTS 

 OF THE REMOVAL OF CAP- 

 ILLARY WATER. 



For the study of the problems of ir- 

 ritability of protoplasm, the Plasmodia 

 of the Mycetozoa afford exceptionally 

 fine material, mainly on account of the 

 large size of the protoplasmic masses at 

 the disposal of the investigator. 



For the study of the geotropic reac- 

 tions, it is necessary to have the cultures 

 so environed that the reactions to light, 

 warmth, currents and chemical substance 

 shall be excluded. The importance of 

 these precautionary methods is well un- 

 derstood by all, for some other stimuli 

 are much more powerful in their effect 

 upon the Plasmodia, than the geotropic, 

 e. g., the r'heotropic and thermotropic. 

 Some of the thermal reactions require 

 explanation, as, for instance, the migra- 

 tion of the protoplasm away from areas 

 of cooling, and consequent condensation 

 — a mass movement which thus takes 

 place in opposition to other physical 

 forces. This phenomenon may be studied 

 under the microscope in the following 

 way: the microscope is so arranged that 

 on one side of its stage a warm stage is 

 placed and kept at a temperature of 75 

 degrees to 80 degrees F., while on the 

 other side, separated by a space of 3-4 

 inch, a cold stage is placed, kept at a 

 temperature of 40 degrees there. Upon 

 these stages the ends of a glass slide, 

 covered by the glass "box to prevent 

 evaporation, is placed and the Plasmo- 

 dium, which should have extended itself 

 over the whole extent of the slide, is 

 studied. It will gradually be seen to 

 collect upon the end of the slide resting 

 upon the warm stage. 



For the study of heleotropic reactions. 



the glass box may be replaced with a 

 light wooden box impervious to light, 

 with a window in its top, which may be 

 closed light tight or be opened for ob- 

 servation. The glass slide is to be re- 

 placed by a wooden plate or a thin 

 glazed tile of suitable size — metal and 

 rubber plates are objectionable — and 

 care must be taken to free the wooden 

 plate from possible chemitropic influence. 

 If it is desired to expose the Plasmodium 

 to light rays from several directions,the 

 glass box may be used covered with 

 black paper in which windows may be 

 cut at pleasure or closed by means of 

 gummed labels cut out of black paper. 



THE EFFECTS OF THE REMOVAL OF CAPIL- 

 LARY WATER, OR HYDROTROPISM. 



The reactions of Plasmodia to a vary- 

 ing supply of water can be easily stud- 

 ied on small Plasmodia on a glass slide 

 provided with a glass box made of cov- 

 er glasses, by cementing the edges of 

 the thin sheets together with marine 

 glue, leaving a drop of glue in each cor- 

 ner to serve as a brace and to more ef- 

 fectually hold the glasses in position 

 under pressure. Such a box may be pro- 

 vided with a hole in the top glass, which 

 may he sealed at any time with a com- 

 mon cover glass smeared with vaseline 

 (glycerine is objectionable in such experi- 

 ments). If the box has an unbroken top, 

 it may be raised over the slide by small 

 strips of glass slide placed under each, 

 or only one end as desired, and in this 

 way the gradual evaporation of water 

 may be secured under observation. If 

 a Plasmodium is transferred to a slide 

 covered with filter paper wet in water 

 and one end of the glass box be coated 

 with a layer of gelatine, the opposite 

 being raised from the slide, the Plasmo- 

 dium will be found to retreat towards 



