PROTOPLASMIC, AMOEBIC, AND OTHER MOVEMENTS 



315 



was presented as at D, namely, the formation of an extremely minute sphere at one end of an elongated mass. This 

 rapidly increased in size, as shown in E, and was then re-absorbed, as at F, by which time another sphere had been 

 formed at the opposite end." 



The cell figured above was from a tentacle of a dark red leaf, which had caught a small moth and was 

 examined by the aid of the microscope under water. Similar movements were witnessed by Darwin in a 

 specimen not immersed. Thus he states : " I placed a fly on a leaf, and when after eighteen hours all the tentacles 

 were well inflected, these were examined without being immersed in water. The cell here represented (Fig. 64) was 

 from this leaf, being sketched eight times in the course of fifteen minutes. These sketches exhibit some of the more 

 remarkable changes which the protoplasm undergoes. At first there was, at the base of the cell 1, a Uttle mass on 

 a short footstalk, and a larger mass near the upper end, and these seemed quite 

 separate. Nevertheless, they may have been connected by a fine and invisible 

 thread of protoplasm, for on two other occasions, whilst one mass was rapidly in- 

 creasing, and another in the same cell rapidly decreasing, I was able, by varying 

 the light and using a high power, to detect a connecting thread of extreme tenuity, 

 which evidently served as the channel of communication between the two. On 

 the other hand, such connecting threads are sometimes seen to break, and their 

 extremities then quickly become club-headed. The other sketches in Fig. 64 

 show the forms successively assumed. Shortly after the purple fluid within the 

 cells has become aggregated, the little masses float about in a colourless or almost 

 colourless fluid, and the layer of white granular protoplasm which flows along the 

 walls can now be seen much more distinctly. The stream flows at an irregular 

 rate, up one wall and down the opposite one, generally at a slower rate across the 

 narrow ends of the elongated cells, and so round and round. But the current 

 sometimes ceases. The movement is often in waves, and their crests sometimes 

 stretch almost across the whole width of the cell, and then sink down again. 

 Small spheres of protoplasm, apparently quite free, are often driven by the current 

 round the cells ; and filaments attached to the central mass are swayed to and fro, 

 as if struggling to escape. Altogether, one of these cells, with the ever-changing 

 central masses, and with the layer of protoplasm flowing round the walls, presents a 

 wonderful scene of vital activity." 



Professor Julius von Sachs gives an interesting representation of the movements 

 of protoplasm in the middle ceU of the hair of a gourd (Fig. 65). 



The protoplasm appears as a finely punctuated mass in which are seen larger 

 bodies, especially chlorophyll granules which contain starch, and, in one case, a 

 small crystal of oxalate of Ume. The movements of the protoplasm are made 

 more apparent by the presence of the bodies referred to. The streaming of the 

 protoplasm gives rise to a beautiful network, which is at once striking and 

 characteristic. 



Darwin in his account of protoplasmic movements, refers not only to the 

 various shapes assumed by the protoplasm within cells, but also to the gyration of (^fr°- ^'^^^^^^ilfi^f r^i.nlui 

 the cell contents. 



As regards the former, protoplasm may be said to move and change shape :— 

 (a) By division and reunion. 



(6) By an advance of its molecules in a particular direction, 

 (c) By a retraction of its molecules in an opposite direction. 



In the former case it exerts a pushing force, and in the latter a pulling force 

 muscles and their sarcous elements. 



In these various movements the volume or quantity of protoplasm remains the same. Change of shape 

 does not imply increase or diminution of bulk. The movements of protoplasm are mherent vital movements. 

 They are also independent movements, and are not the result of irritability or external stimulation. Neither are 

 they to any extent, the product of elasticity. While elasticity is a property peculiar to all bodies, orgamc and 

 inorganic it plays quite a subordinate part in vital movements and mamfestations-mdeed the influence exerted 

 by it is in the majority of cases, so trifling that it may almost be disregarded. It is the life which inaugurates, 

 regulates and terminates all movement in plants and animals ; the life acting as a prime mover and not delegating 

 its work, to any appreciable extent, to elastic materials and properties which it must evoke and control. 



Fig. 65. — Longitudinal section of 

 the middle cell of a hair of the Gourd 



clump enclosing the nucleus of the 

 cell ; c, streaming filaments of proto- 

 plasm in active movement, and carry- 

 ing chlorophyll corpuscles (containing 

 starch in their substance) ; d, a crys- 

 tal being hurried along (after Sachs). 



Similar powers are possessed by 



