March 1, 1899/ 



KNOWLEDGE. 



57 



motion of currents of protoplasm ; and, secondly, the 

 advance of the entire mass of protoplasm. 



Under a microscope currents are seen to be established 

 in the endoplasm, generally up or down the lines of advance 

 of the Plasmodium ; the letters st in Fig. 4 indicate some 

 of these currents. The granules stream iu one direction ; 

 then pause, from sixty to ninety seconds (in the case of 

 healthy plasmodia) ; then the current turns and streams 

 in the opposite direction. These streams sometimes unite 

 and sometimes divide. It is familiar that protoplasm when 

 enclosed in cells often exhibits movements, as in the well- 

 known case of the Chara, but then the movements are 

 naturally constrained by the cell walls ; in the free 

 protoplasm of the mysies no such restraint exists. 



If the peripheral edge of an advancing plasmodium be 

 examined, there will be found in advance of the granular 

 endoplasm a strip of the colourless and perfectly transparent 

 ectoplasm, of which we have already spoken ; it runs like 

 the foreshore along the coast of the body. Into this from 

 time to time a granule will be seen to advance, and then 

 another granule, and so on till the line of the land has 

 been pushed out into the foreshore, and the foreshore itself 

 is moved forward into the sea. In this way the front line 

 of the whole plasmodium advances, and as the rear of the 

 Plasmodium is drawn back in the line of advance as the 

 front line is pushed forward, the whole body of the plas- 

 modium gradually changes its place and moves forward. 



It is a very striking thing to watch these forward move- 

 ments of the granules. You seem to see in a minute and 

 most intimate form the locomotion of living things ; and, 

 moreover, you perceive an internal movement of part, 

 resulting in a movement in space of the whole organism. 

 Mr. Spencer has said that " we have as yet no clue to the 

 mode in which molecular movement is transformed into 

 the movement of masses in animals." Does not the 

 motion which we have described offer, if not a clue, yet a 

 visible example of such transformation ? Be this as it 

 may, the mystery of motion remains just the same ; there 

 is the same antinomy between sense and reason — the one 

 says that there is motion, the other that it is impossible. 



'* lo diro cosa incredibile e vera." 



It must not be supposed that it is only on the surface of 

 dead wood or leaves that the plasmodia of myxies move. 

 Sometimes, and especially under the influence of cold, 

 they retreat downwards, and the Fulujo, a species which 

 lives on tan and is known as the Howers of tan, will, 

 under this influence, disappear from the surface of a heap 

 and retire to the bottom of it. Cold or other unsuitable 

 conditions seem to cause them sometimes to retreat into 

 the wood to appear again under more favourable circum- 

 stances. Some Plasmodia inhabit the interior of dead 

 wood, and only appear on the surface for the purpose of 

 fruiting ; in the search for a suitable home for reproduction 

 it has been thought that they move away from damper to 

 drier spots, and they certainly often produce their sporangia 

 in the dry air and in high positions. It has been thought also 

 that light has a tendency to make the plasmodia ascend 

 and darkness to descend. Sometimes a plasmodium will 

 ascend a tree or a post for a foot or more, and a species 

 known as Lycogala epidendron is said always to affect the 

 highest point of the substance on which it rests. It is 

 by no means infrequent for plasmodia to leave the dead 

 wood on which they have been living and to ascend the 

 stalks of flowering plants, or to spread over mosses, and 

 often we have been surprised at the distances travelled by 

 Plasmodia in a few hours. The appearance, we may 

 remark in passing, presented by the sporangia of delicate 

 myxies on the leaves of mosses or blades of grass is 

 sometimes very beautiful. 



Plasmodia, as we have said, sometimes move in an 

 upward, sometimes in a downward direction ; in a seed, 

 as we know, these two tendencies are separated, and the 

 radicle tends to grow in the direction of gravity, and the 

 plumule against it ; in the myxies it would seem as if the 

 same protoplasm at one time had the one tendency, and at 

 another time the other. Perhaps, in passing, we may 

 observe that the fact that plants and trees for the most 

 part grow upward — i.e., against the force of gravity — is one 

 worth a good deal of thinking about, and when we look at 

 the mass of fluid and solid matter raised every year, 

 especially in the springtime, against the constant operation 

 of the force of gravity, we get a notion of the magnitude 

 of a force exerted by plants, to which we can assign no 

 other origin than life, and give no other name than that 

 of a living force. 



It has been found with regard to the plasmodium of the 

 flowers of tan that it has a curious tendency to move 

 against the flow of water ; thus, if one end of a piece of 

 filter paper be placed in a vessel filled with water and the 

 other on the table, so that the water flows downward, the 

 Fuliyo wUl move up the paper, and if the paper be so 

 arranged that the water shall move up the paper, the 

 Fuliyo will move down. 



Some observers believe that the myxie takes only such 

 food as comes in its way ; Mr. Lister believes that it uses its 

 vibrating cilia to detect food ; whilst others think they have 

 observed that food exercises an attraction on plasmodia 

 and influences their movements ; thus, to return to the 

 flowers of tan, a piece of tan or of wood steeped in tan has 

 been seen, according to some observations, to induce the 

 Plasmodium to draw itself towards it, and that without 

 reference to its position as regards the force of gravity. 

 There seems no reason to doubt the accuracy of these 

 observations. Here, then, we see in the primitive form of 

 naked protoplasm that search after food which exercises 

 so enormous an influence on the whole animal and vegetable 

 world as well as in the social a£fairs of man. How, one 

 cannot help asking, is the plasmodium made aware of the 

 proximity of its appropriate food '? Has it some rudimen- 

 tary perception — some common sense, of which sight, and 

 smell, and taste are only more specialized forms '? What 

 the Plasmodium does in the equaUy near presence of two 

 equally attractive morsels we do not know ; but we do not 

 believe that it would starve. 



Sunshine is, again, a condition which seems to exert 

 an influence on the movements of plasmodia. If a glass, 

 on which the network of a plasmodium is spread, be partly 

 exposed to the sunlight, it has been observed to withdraw 

 to the shaded parts, and yet when the time comes for 

 the sporangia to be produced it would seem in some species 

 as if there was a movement towards surfaces exposed to 

 light. But, according to the observations of Mr. Lister, 

 light apart from direct sunshine does not affect the 

 movements of plasmodia. 



The Plasmodium has been found to be sensitive not 

 only to sunlight, to dampness and dr3rness, to heat and 

 cold, but to the influence of chemical substances : the 

 weak solutions of some chemicals having been observed to 

 render it more fluid, whilst stronger solutions of the same 

 substances have made it contract or perish in parts. This 

 sensitiveness on the part of the plasmodia to so many 

 influences must, it would appear, render very delicate the 

 conditions under which alone myxies can succeed in the 

 struggle for existence. Furthermore, it would appear that 

 in the seiectiDU of places for the production of the sporangia 

 they have to select situations affording enough atmospheric 

 exposure to ripen the spores, and enough moisture to enable 

 the swarm spores to swim and move about, and it is no 



