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necessary, and in aquatic creatures some similar contrivance is 

 found, the most common, probably, being the power of rotation 

 on the long axis. This rotation produces a compensating effect 

 for any little irregularities in motive power ; and although 

 the actual path is really a long spiral, its general direction is 

 practically a straight line. Passing on to deal with the actual 

 methods of locomotion found in the organisms under discussion, 

 the lecturer described at some length the means of progression 

 observed in Amoeba. Examples of amoeboid movements are very 

 common among the class to which Amoeba belongs — that is, 

 the Rhizopods, and including the Foraminifera. Owing to 

 the observations and experiments of Biitschli, Rhumbler, 

 and others, it is probable that in its main features amoeboid 

 motion is essentially a physical phenomenon, depending chiefly 

 upon changes in the surface-tension of the naked protoplasm 

 of these organisms. It was pointed out that while usually the 

 movements of pseudopodia are very slow, and are ineffective 

 except when in contact with solid bodies, yet in a few forms 

 the pseudopodia are long and fairly vigorous in movement, 

 and may be taken as transition forms between typical 

 pseudopodia and the flagella or whip-like organs next to 

 be considered. A flagelluru may be defined as a permanent, 

 motile, whip-like extension of the living protoplasm, capable of 

 moving the whole organism to which it belongs, and capable 

 of independent motion if, as is sometimes the case, it is 

 accompanied by other flagella. Some flagella have been shown 

 to have connection w T ith the nucleus of the cell ; but this is ex- 

 ceptional. It is considered that the motive- power of a flagellum 

 resides in the flagellum itself. Mr. Scourfield then proceeded 

 to deal with the difficult question as to how a single whip-like 

 organ produces motion in a straight line of the organism to 

 which it belongs. The only reasonable explanation seemed to be 

 that a succession of waves are set up, travelling backwards along 

 the filament. These waves are not confined to one plane, but 

 rotate as they progress, thus throwing the flagellum into a 

 spiral form — the effect produced being, in fact, similar to that 

 in a rotating corkscrew, with the essential difference that the 



