1184 



Journal of Applied Microscopy 



animals swam towards the light until they encountered the acid solution, and 

 then instead of turning back stayed there till they were killed. In conclusion 

 the author gives a rather unconvincing answer to certain criticisms of his 

 earlier work. 



In the paper several useful pieces of apparatus for phototaxis work are 

 described. The method of changing the direction of the light rays impinging on 

 the animal without disturbing any of the other conditions seems especially 

 valuable and will be described in detail. " A tin trough 8 x >4 x ^ inches 

 (T) mounted on a wooden base was painted dead black ; at either end of this 

 trough a glass box, A, A', containing alum solution was placed. Screens, S, S', 

 were arranged so that side rays and reflected light were cut off, and the trough 

 was illuminated exclusively by rays parallel with its long axis coming through 

 holes six inches high and two inches wide cut in the screens, S, S'. At either 



end, ten inches from S and 

 S' respectively, was a 

 Welsbach burner, L, L'. 

 For observations this appa- 

 ratus was set up in a dark 

 room. After the trough had 

 been filled with water and 

 the screens s, s', which 

 shut off all light, had been 



S' 



\y}/////////m////////////}a\ 



placed in position, an animal was carefully dropped into the middle of T. One 

 of the screens (s) was then removed and the animal responded usually with a 

 -f reaction, — it moved toward the end from which the screen had been removed, 

 that is, toward the light. As soon as the animal came within two centimeters of 

 the + end of the trough, s was quickly replaced and s' removed, thus giving light 

 from the opposite direction without the inconvenience of moving the burner. 

 By this means it could easily be observed whether the response was continued 

 as before or reversed." R- ?• 



Piitter, A. Studien iiber Thigmotaxis bei The author deals in a thorough and 

 Protisten. Arch. Anat. u. Physiol. Physiol. exhaustive way with the effect of COn- 

 Abth. Suppl. Bd. IQOO: pp. 243-302. .,,.,,,. 



tact with solid bodies on the reactions 



of the Protozoa. After a brief historical introduction and description of methods 

 employed, the reactions of a large number of Protozoa, including nearly all the 

 main groups from the rhizopods to the hypotrichous ciliates, are described in 

 detail. Positive and negative forms of thigmotaxis are distinguished according 

 as the animal remains in contact with a solid body which it encounters, or moves 

 away from it. The positive reaction displays two forms or factors. The first 

 factor is the one which affects the locomotor organs (pseudopodia, fiagella or 

 cilia) and results in a lessening or inhibition of their movement. The second 

 factor in the thigmotaxis is the secretion of a sticky slime which helps to fasten 

 the animal to solid bodies. This secretion factor is very evident among the 

 rhizopods, less apparent among the flagellates and ciliates where the first factor 

 is most important, and finally it is the most essential phenomenon in the thigmo- 



