Reactions of I so pods 44 1 



the water in the larger dish to keep the temperature from rising. 

 When necessary the excess of water was removed. 



The animals were given fifteen minutes or longer to become 

 somewhat settled in their new quarters. When thev had appar- 

 entU' begun to act and move about normalhs the test was begun. 

 First the largest bristle was used and the Asellus and Caecidotea 

 gently touched on various portions of the body and the sensitive- 

 ness as indicated by the anmials' movements noted. No record 

 was made until after several trials unless the reaction was unmis- 

 takable at once. First, for example, the Asellus was tested with 

 one of the bristles upon the flagella of the antennae, then the Cae- 

 cidotea was tested for the corresponding part. In like manner 

 similar tests were made for other parts of the body. No special 

 sequence was followed in testing the various portions of the body. 

 Sometimes one portion was tested first and sometimes another 

 But the corresponding parts of the two species were always tested 

 one after the other. 



The response to the various stimuli indicating corresponding 

 grades of sensitiveness were designated by the following terms — 

 extremely responsive, strongly responsive, fairly responsive, 

 slightly responsive, and not responsive. An animal was considered 

 extremely responsive if the movement was prompt and decidedly 

 vigorous; strongly responsive if the response was slightly less 

 prompt and vigorous than indicated for the extreme responses, 

 but more vigorous than the normal movements of the animal 

 fairly responsive when the reaction resembled the normal move- 

 ments of the animal in rapidity and vigor; slightly responsive 

 when there was any observable response less active or pronounced 

 than the normal movements; and not responsive if no movements 

 were observed after several attempts at stimulation. The follow- 

 ing table will serve to illustrate the tests made and the manner 

 of recording them. 



This record (Table i) is typical of the difi-erences in sensitive- 

 ness to mechanical stimulation between the two species. It will 

 be noted that whereas to bristle No. i the Asellus was very respon- 

 sive, to bristle No. 3 it w^as scarcely responsive at all. With 

 Caecidotea the extreme responsiveness was as marked with the 



