318 EECORD OF CURRENT RESEARCHES RELATING TO 



The " Fasergrubclien " or sterile conceptacles are regarded by Mr. 

 Bower as incomplete sexual conceptacles. The male and female con- 

 ceptacles are indistinguishable in their early stages, the first differen- 

 tiation making itself apparent in a difference in the nature of the 

 hairs which line them, especially of the neutral hairs and tliose which 

 do not produce antheridia or oogonia. It is the rule that no branching 

 occurs in the neutral hairs of the female conceptacle ; while in the 

 male conceptacle, even before the formation of the antheridia, the 

 hairs branch according to a monopodial racemose system. The 

 antheridia and oogonia he regards as, in most cases at least, morpho- 

 logically identical in their origin. 



Influence of Light on the Movements of Desmidiese and Swarm- 

 spores.* — With the exception of a single observation in Braun's 

 ' Verjiingung in der Natur,' hardly any attention has been paid to 

 the influence of light on the movements of Desmids. E. Stahl has 

 now made it a subject of investigation, directing his attention chiefly 

 to Closterium moniliferum, specimens of which he enclosed in a glass 

 cube with walls about 1 cm. in height, changing the direction of 

 the incident light by means of mirrors. 



It was soon evident that the dii-ection of the light exercised a 

 material influence on the position of the longer axis of the cell, this 

 axis having a tendency to place itself in the direction of the rays of 

 light ; and that there is also a polarity between the two halves of the 

 cell, in consequence of which one is attracted towards and the other 

 driven away from the source of light. The direction is subject to 

 alternations in consequence of which the cell is continually shifting 

 its position through an angle of 180°, presenting each end alternately 

 to the light. In one experiment, at a temperature of 33° C, the time 

 occupied by this reversal of position was from six to eight minutes ; 

 in another, where the temperature was 17° C, from fifteen to thirty- 

 five minutes. In addition to this reversal, there was also a slow move- 

 ment of the individual along the bottom in the direction of the source 

 of light. When the light is very intense, the conditions are reversed, 

 and the cell places itself with its longer axis at right angles to the 

 direction of the light. 



Dr. Gobel has made similar experiments on another Desmid, 

 Micrasterias rotata, which was found to place itself with the plane of 

 its disk at right angles to the direction of the rays of light. The direc- 

 tion of the band of chlorophyll in which the nucleus is embedded 

 varies with that of the incident light. 



In Strasburger's work on the influence of light on the movements 

 of swarmspores,t he applies the term phototaxis to the law by which 

 these bodies place themselves with their larger axis in the direction of 

 the rays of light, calling the swarmspores themselves phototactic. 

 Phototactic swarmspores are, according to him, either photometric, 

 when they turn sometimes one end, sometimes the other end towards 

 the light, or aphotometric, when the same end is constantly turned 



* 'Verb, physikal.-med. Gesell. Wiirzburg,' xiv. (1880) p, 24. 

 t See this Journal, ii. (1879) p. 307. 



