§3] 



ELECTROTAXIS 



147 



and '95), and Blasitjs and Sch-weizb'r ('93); and among 

 Vertebrates by these authors and also Hebmann ('85 and '86), 

 EwALD ('94, '94% and '94"), Hermann and Matthias ('94), and 

 Waller ('95). The number of species investigated has been 

 considerable. I give below a table of the Invertebrate genera 

 studied and the sense (+ or — ) of their response at the given 

 intensity of currents. Barely rough quantitative expression 

 of strength of current can be deduced from Nagel's paper. 

 Where no data are given the currents are supposed to be of 

 intermediate strength. N. stands for Nagel, B.S. for Bla- 

 sitjs and ScHWEizER. The numbers which follow give the 

 year of publication and the page. 



TABLE XV 



Specific Name. 



Mollusca : 



Limnsea stagnalis . . .... 



Var. other. Gastropoda (probably) 



Annelida : 



Lumbricus ... 



Tubif ex rmilorum 



Hirudo niedicinalis . . . 

 Branchiobdella parasitica 



Crustacea : 



Cyclops 



Asellus aquaticus 



Astacus fluviatilus 



Insecta : 



Notonecta . 



Corixa striata 



Dytiscus marginalis 



Hydrophilus piceus . 



Steength of 



CUEEENT. 



weak 



0.8 3 



strong 

 strong 

 0.48 



1.9 S 

 1.9 8 



Sense of 

 Response. 



+ 

 + 

 + 



+ ? 



+ 



+ 



AUTHOEITT. 



N. '95 



N. '92»; '95 



N. '95, 626 

 N. '95, 631 

 B.S. '92; 516 

 B.S. '92, 516 



N. '92, 629 

 N. '95, 633 

 B.S. '92, 518 



N. '95, 636 

 N. '95, 636 

 B.S. '92, 519 

 B.S. '92, 519 



From this table it appears that Mollusca and Annelida are 

 usually negatively electrotactic to a current of medium inten- 

 sity, while Arthropoda are mostly positively electrotactic to 

 such a current. It is noteworthy, however, that two quite 



