154: Proceedings of the Iloyal Physical Society, 



grouped together ; while in others again, as many as nine or 

 ten are detected in two clusters (fig. 2) ; but in these cases 

 I am disposed to think that the individual is composed of two 

 animals in a state of conjugation, as it is always elongated 

 and slightly constructed between the masses of nuclei. 

 These animals, from their large size (from Jth to Jth of an 

 inch in diameter), can be readily transferred to a flat cell 

 under the microscope, when the excessively rapid movement 

 of the sarcode affords a very interesting and astonishing- 

 spectacle. Each of the great pseudopodia consists of a 

 number of streams, some rapidly coursing outwards, others 

 passing inwards more slowly, and dragging along masses of 

 diatoms, minute alga, and infusoria. Even in the most 

 minute branches of the periphery a double movement, in 

 opposite directions, is clearly visible under high amplifica- 

 tion. In fact, the whole organism reminds one of a great 

 central railway station, the meeting-point of numerous con- 

 verging lines, to which an unceasing flow of traffic is ever 

 tending. A rude touch, as with a needle point, to the animal 

 itself, has the effect of arresting the outward movement, 

 and of determining the whole flow rapidly to the centre. 



An explanation of the movements of the pseudopodia is 

 extremely difficult ; and indeed the same may be said of 

 the nature of the pseudopodia and whole*; structure of the 

 rhizopod itself. We find it difficult to believe that a mere 

 mass of gelatinous slime, apparently homogeneous, can 

 determine such purpose-like and varied movements through 

 the wide-spread and ever varying extension of its network, 

 and can instantly arrest or alter these movements at will, or 

 from the effect of external stimulus. Accordingly, Eeichert 

 has dissented from the sarcode theory, first promulgated by 

 Dujardin and strongly insisted on by Schultze, and is of 

 opinion that the pseudopodia consists of bundles of exces- 

 sively fine filaments — so fine " that a perceptible thickening 

 scarcely appears when several filaments come together, or 

 when the magnifying power is raised from 450 to 700 

 diameters." He considers " that when the animal first ex- 

 tends its pseudopodia the more simple radiate arrangement 

 predominates ; soon afterwards the apparent ramifications 



