708 



SCIENCE. 



[N. S. Vol. XXIII. No. .592. 



fully pulled out with a pair of fine forceps 

 into a few drops of one-half -per-cent. solution 

 of common salt upon a glass slide. The intes- 

 tine is then opened, and the contents scraped 

 out and examined. 



A preliminary attempt by the writer and his 

 assistants to use Amosha hlattce as a laboratory 

 subject with a class of a hundred and forty 

 beginners did not meet with success, but little 

 diiSculty has been experienced in demon- 

 strating it to small groups of students. Usu- 

 ally at least one in every four or five of the 

 cockroaches which we have examined this 

 winter has proved to be abundantly infested 

 with the amoeba. 



Ammha hlattce is a rapidly moving organism, 

 without pseudopods, and is of especial interest 

 from the fact, which Ehumbler has demon- 

 strated and which I have been able repeatedly 

 to confirm, that backward peripheral currents 

 occur in the endoplasm in addition to the 

 axial forward stream. 



The currents resemble those of a drop of 

 oil or of other non-living fluid, in which the 

 surface tension is unequally distributed. Such 

 a drop contains an axial current, which flows 

 in the direction of a certain area upon its 

 surface over which the surface tension is 

 diminished, turns outward in front, and forms 

 backward superficial currents like a fountain. 

 Hence the term ' fountain currents ' has been 

 applied to this phenomenon. In A. hlattce 

 the backward superficial currents usually do 

 not come to rest, as in the simpler fountain 

 currents, but unite at the rear and enter the 

 central forward stream, establishing thus that 

 which Rhumbler calls a ' fountain whirl ' 

 (Tontanenwirbel')- It is on the existence 

 of such currents as these in Amaha and Pelo- 

 myxa that Biitschli, Rhumbler and earlier 

 writers have based the theory that amoeboid 

 movement is due to diminished tension over 

 a certain area of the surface, since drops of 

 non-living fluid, e. g., oil or chloroform, sub- 

 merged in water and acted upon in such wise 

 that the tension over a certain area of the 

 surface is suddenly diminished, flow in pre- 

 cisely the manner above described. 



The reader will recall that Jennings,^ in 

 his recent paper on the ' Movements and Re- 

 actions of Amoeba,' denies the existence of 

 ' fountain currents.' His careful and long- 

 continued studies were based, however, prin- 

 cipally on A. Umax, A. proieus, A. angulaia 

 and A. verrucosa, and did not include A. 

 hlattce or members of the genus Pelomyxa, in 

 which such currents have been found by other 

 observers. 



Locomotion in Amoeba verrucosa, and in the 

 other species which came under Jennings's 

 observation, is a rolling forward, as of a blad- 

 der half filled with water, or of a bag half full 

 of shot, that is pushed over a flat surface. 

 In this case the entire endoplasm continually 

 streams forward, and the ectoplasm roUs on- 

 ward around the endoplasm. A particle of 

 soot, caught upon the surface of the advancing 

 AmAxiha, is carried forward until it reaches 

 the anterior edge of the animal, then down- 

 ward beneath the body, where it remains quiet 

 until the Am^oiha has passed completely over 

 it, and it lies beneath the posterior edge. It 

 is then carried upward and again forward to 

 the anterior margin. 



Rhumbler concedes that this form of loco- 

 motion can not be due to inequality in ordi- 

 nary surface tension, and attempts to explain 

 it as the result of unequal pressure at different 

 parts of the surface, which is brought about 

 by the unequal contraction of the ectoplasm 

 as the result of gelatinization. The endo- 

 plasm at the anterior end of an Amceha in 

 motion, according to this view, meeting there 

 less resistance than at other points from the 

 pressure of the gelatinizing and contracting 

 ectoplasm, tends to burst forth from its con- 

 fining envelope, and to become transformed 

 into ectoplasm. Elsewhere, particularly at 

 the posterior end of the organism, the reverse 

 is supposed to take place, viz., ectoplasm is 

 converted into endoplasm. An explanation of 

 the lessened resistance of the ectoplasm at the 

 anterior margin is sought in the stretching of 

 the outer layer in that region, brought about 



' Jennings, H. S., '04, ' Contributions to the 

 Study of the Behavior of lower Organisms,' Car- 

 negie Institution, Washington. 



