in the Pseudopodia of the Rhizopoda. 403 



fidence in the correctness of the dogmas of the theory of primor- 

 dial slime, sarcode, or protoplasm, must admit, after some con- 

 sideration, that the picture of a fluid and flowing mass may also 

 very easily be produced in separated and not fluid, but solid or 

 semisolid (festweichen) masses whenever two conditions are ful- 

 filled : — 1, when the surface of such bodies brings an alternate, 

 more or less regular play of elevations before us in such a man- 

 ner that we are led to conceive a motion like that of waves in 

 water ; and 2, when bodies really separate, but not distinguish- 

 able as such at their mutual points of contact, are constantly 

 changing their relative position, and under these circumstances 

 present themselves as a mass varying at pleasure in form and 

 limits, and possessing properties appertaining to fluid sub- 

 stances. From the point of view which I am convinced is to 

 be maintained, if not alone, still especially, in regard to or- 

 ganisms, the impression made by the phenomena of motion in 

 the pseudopodia becomes essentially different ; the lustre of the 

 dogmas respecting the sarcode-theory is very soon lost, and the 

 heresy then becomes clear and unmistakeable. 



In order, however, to avoid being misled by the deceptive 

 image, it is necessary in this, as in other cases, to take up the 

 microscopic analysis of the individual filaments, and at first to 

 disregard as much as possible their proteus-like complicated 

 mass. According to my observations upon the nature of the 

 individual f laments, the following statements may be made: — 



The pseudopodia, which, when fully extended, measure six or 

 eight times the greatest diameter of the body, form at their free 

 extremities (where they may with the greatest certainty be found 

 simple and single), extraordinarily fine filaments, even under the 

 highest powers of the microscope. To give some notion of their 

 fineness the observation will suffice, that a perceptible thicken- 

 ing scarcely appears when two or three filaments come together 

 and apparently fuse into one, or when the magnifying power of 

 the instrument is raised from 450 to 700 diameters. For the 

 same reason nothing definite can be said as to whether they are, 

 as they appear to be, perfectly cylindrical or more or less flat- 

 tened. They appear to be everywhere of uniform thickness. 

 Apparent or real local thickenings occur in consequence of move- 

 ments of contraction, to which I must revert hereafter; I must 

 likewise defer the discussion of the question whether, besides 

 decidedly simple filaments, branched ones occur, issuing from 

 the former by movements of contraction. The individual ex- 

 tended filaments consist of an apparently colourless, transparent, 

 hyaline substance, which at the extreme ends, where they may 

 most readily be observed singly, possesses an index of refraction 

 differing very little from that of the surrounding fluid (sea- 



27* 



