552 ^'^^ £OrANICAL MAGAZINE. fVoi. xxx. n... sss 



Die Organismen vandern, um die Liingsachse rotirend, lasch aufwarts, wie Schiffe ia 

 Kiellinie genaue Kiclituiig haltend. Plotzlicli sistiren eiiiiiic der obcreu ihrc Bewegung, 

 man iiat den Eindnick als oh raomeiitan die Maschine still stand e ; nun folgen sie 

 ihrer eigenen Schwerc mid sinken rait dem Hinterende voran abwiirts, dabei trefl'en 

 sie auf die vertikal uiiter ilinen noch aufwiirta steuernden Genossen, reissen diese 

 rait und so sinkt ein Kniiuel von 10-20-30 Kugeln abwiirt^. Man glanbt, sie wiirden 

 in kurzer Zeit auf dem Boden anlangen, aber plotzlich wird der Fall aiifgehalten, 

 einen Moment liegt der Kniiuel still, dann entwirrt er sicb rascli und eine Kugel nach 

 der andern selzt ihren Curs wieder vertikal aufwiirts, die Kiellinie ist hcrgcslellt, nm 

 nach kurzer Zeit von Neuem durcli den Absturz der Fiihrer gestort zu werden. 

 Die Kniiuel fallen in den verscliiedcnen Tbeilen des (refUsses verschieden tief; es 

 gelangen die an der hellen Seite auf- und abwandernden niclit so weit nacii unten, 

 als die in etwas geringerer Helligkeit befindlichen. Die Fallbewegungen werden offen- 

 bar sistirt, sobald eine Zone von bestimmter Intensitat des Lichtes erreicht ist." 



In the present case the innumerable number of swarmspores 

 in the relatively small space and their minute size made the 

 accurate observations more difficult than in Volvox which is 

 much greater than Chlamvdomonas. The phenomenon was most 

 well demonstrated by cooling the water. To make clear the 

 relation between light and this peculiarit}', the following ex- 

 periment was undertaken in the dark room. 



If the matter just described is simply due to the convection 

 current induced b\' the difference of temperature of the different 

 parts of water and not due to the response of organism toward 

 light, it would be possible to give rise at will to the same 

 phenomenon by shutting out the light and changing the ph^'si- 

 cal condition of medium. Firstly I cooled one side of the 

 flask by means of ice. After a few minutes some few lines of 

 downward movement of organism appeared at the very side, 

 to which ice brocks were applied. Secondly to make one side 

 of the flask warm a piece of hot " Konn\'aku '" (52° c) was 

 attached to the latter. This warming experiment also proved 

 efficient to produce a few lines of downward movement of or- 

 ganisms at the opposite side of the ffask of the warmed culture. 

 In both experiments the temperature of the culture medium was 

 25° C. These observations were made in the dark room, only 

 admitting the weak light of the portable electric search lamp 



Ij "Konnyaku" is a kind of .Japanese food prepared from the tubers of 

 Hydro!^me Rivieri. It is elastic and greyish translucent like agar-agar, but is unlike 

 the latter insoluble in hot water. 



