iMICHIGAN ACADEMY OF SCIENCE. 69 



remains that it is often so found. After watching the operation a number 

 of times, it is my conclusion that the phenomenon is due merely to the 

 shape of the shell and filament and the nature of the engulfing force. 

 An end of the strand is encountered and ingested. As it strikes the 

 dome of the shell, it bends to one side or the otlier, and continued exertion 

 results in the coiling of the filament as the most conservative mechanical 

 mode of disposition. 



As a matter of fact, similar cases are observed in the inorganic vi^orld. 

 Calkins (10) states that a drop of chloroform will draw in a thread of 

 shellac in the same way, as will also egg albumen with gum arabic. The 

 implication is that many of the vital processes of lower forms, like in- 

 gestion and excretion, are not different in kind from physical processes 

 occurring quite outside the organic realm. 



GAS VACUOLES. 



The possibility of another mode of locomotion tl»an that of pseudopo- 

 dial progression lias received considerable attention. Long since, at 

 least by the time of Engelman ('69), gas bubbles were observed in 

 Arcella, which grew in size and then subsided, apparently without refer- 

 ence to external conditions. Since tliat time these liave been considered 

 as hydrostatic organs, capable of raising or lowering the body in the 

 water. Whether or not this function is purely a myth is not yet clear. 



The gas bubbles appear in all jilaces in the body, are irregular in shape, 

 and have no constant relation to the nucleus and contractile vacuoles. 

 Khainsky (10) remarks that the change in volume usually occurs in 

 all the bubbles of one individual at the same time. This has its excep- 

 tions, as not all the bubbles change size at the same rate. 



The nature of the gas contained has been variously regarded as oxygen, 

 carbon dioxide, and atmospheric air. Dr. Khainsky (op. cit.), who seems 

 to be the only recent worker on the subject, declares the gas to be neither 

 oxygen, carbon dioxide nor sulphur dioxide, as indicated by appropriate 

 tests. Furthermore he states that they do not appear in cultures where 

 there are no algae, that they grow at niglit and diminish by day, and 

 are never present in young individuals. Finally he surmises that the 

 bubbles gain access to the shell by the animal climbing to the surface 

 film and elevating the shell into the atmosphere by pseudopodial action. 

 His conclusion is equally remarkable: "The gas bubbles play no physio- 

 logical role with Arcella, and for the organism itself are only harmful. 



The Arcellas which contain gas vacuoles always die." "In 



den Fallen wo die Arcellen mit Blasen an irgendeinem Gegenstand 

 anhaften, pressen sie die Gasblasen durch die Schale heraus," assuming 

 the shell to be porous. 



