82 J. S. SZYMANSK1 



The base of the apparatus is formed of 29 insulated copper 

 plates, each 0.5 cm. wide. The distance between plates is 0.1 

 cm. The unpaired plates are connected with a long plate on 

 the one side of the base and the paired plates with a similar 

 plate on the other side. The two long plates are connected 

 with an induction apparatus and this, in its turn with an accumu- 

 lator of 2 volts. By this manner of setting up the current, all 

 the non-paired plates form one electrode and all the paired 

 ones a second electrode. Above the base is a bottomless glass 

 box, (Fig. 1 ac) 19 cm. long, 2.7 cm. wide and 8.5 cm. high. 

 Two-fifths of this box is entirely covered with black paper 

 (Fig. 1 db). 



In order to determine at first to what degree cockroaches 

 are influenced by the electric shock, I removed the glass box 

 and placed in its stead another bottomless glass box, 16 cm. 

 square, in order to prevent the animal from escaping. I then 

 put a cockroach into this second glass box and observed that 

 after running about for some time the animal came to rest. 

 I then turned the electric current upon it. I began with a 

 very light shock (distance of coils being 19 cm.) and increased 

 the intensity gradually. The first visible reaction set in at an 

 average of 14.5 cm. distance of the induction coils. This reac- 

 tion showed itself by the animal suddenly moving about, run- 

 ning to and fro and trying to crawl up the glass walls. The 

 intensity of the current at 12—13 cm - distance of the coils seemed 

 to be most effective, and this intensity was used in all subse- 

 quent experiments. A higher intensity caused temporary paraly- 

 sis, if used for a time. 



All the animals I experimented upon were male larvae, 4 

 about one and a half years old, whose parents had been bred 

 and kept in the Vienna Biological Institute. 



During the definite experiments, and at the end of each 

 series of experiments, the floor of the apparatus and the w r alls 

 of the glass box w r ere thoroughly cleansed with cotton wool 

 moistened with alcohol in order to deodorize the apparatus. 



After having replaced the covered glass box, Fig. 1, on the 

 base, I started the definite experiments now to be described. 

 A cockroach was placed in the lighter part of the box ; it imme- 



4 Mature animals differ externally from old larvae only by the presence of the 

 pair of rudimentary wings. 



