Macbride: Ways of the Slime-Mould 331 



beginning the ascent of the overhanging face. Over the boulder 

 I turned a tight, wooden box. In course of a few hours I found 

 on the summit of the boulder, eight or ten inches high, as fine an 

 TEthalium as anyone could wish to see. At the same time the 

 vertical box wall showed plenty of belated, ascending streams, no 

 doubt intended for a second JEthaliam somewhere within the over- 

 turned box. 



I have cited this last example because it seems to me to afford 

 the simplest illustration we are likely to have, at least in the field, 

 of the problem with which biophysics has to deal. The Plasmo- 

 dium, i.e., the TEthalhtm of the physicist, in every case, we may 

 assume, the same, — a mass of naked protoplasm, made up of myriads 

 of minute, almost undifferentiated living cells, so associated as to 

 be undistinguishable, at least in life, — is to the physicist a fluid, 

 homogeneous, only slightly more dense than water, if at all ; subject 

 to desiccation, but not at all aquatic, requiring for translative move- 

 ment, not a wet surface, not at all, — such perhaps in a measure pro- 

 hibitive, — but probably best an invisible film, such as the moist 

 atmosphere of summer might lend to any slightly cooler surface; 

 too dry, doubtless as a matter of course, unfavorable. Of course, 

 there can be no movement here as elsewhere, unless there is re- 

 sistance, some point d'appui ; so having considered the athlete, let 

 us now consider the Matterhorn of his ambition. 



Of the three instances of accomplishment, the second, the Fries- 

 ian episode, may be now neglected as offering no special matters 

 of distinction ; if we are to overcome gravitation at all, the living 

 stem of the growing plant would seem to afford highway most 

 practicable, covered, we may suppose, with inequalities, points, 

 projections of every sort as it surely is. This seems really of 

 small advantage, if not a hindrance, to be surmounted ; the glaucous 

 glabrous shaft of Impatiens found in practice, useful for ascent as 

 any other. 



Let us study, then, the lake-side case. Here the journey was 

 made around the blunt edge of an overhanging shelf ; the action 

 of gravity not only contrary to the general course of progress, but 

 also in part (vertically) athwart it, as if to pull the climber from 

 its hold. Nevertheless, as stated, and in abundant measure, the 



