442 



A. M. Banta 



small bristle. No. 3, as with No. i. There are noticeable individ- 

 ual differences in both species, but in these tests the most respon- 

 sive Asellus was less so than the least responsive Cqecidotea. The 

 two individuals whose reactions are recorded in Table I repre- 

 sent for the two species about the average conditions as far as 

 reactiveness to mechanical stimulation is concerned. 



A series of ten pairs of individuals was tested and the results 

 are summarized in Table II. 



TABLE I 



Reactions oj Asellus communis, No. 2, c?, length, 10.8 mm.,and oj Cacidotea stygia,No. 2, c?> length 

 10. 2 mm., to stimulation by bristles. 



October 30, i<)05. Temperature of \A'ater, i 1.4° C. 



Bristle A'o. I (A pig bristle O.J mm. in diameter) 



1. Flagella of the an- 



tennae 



2. Basal segments of 



the antennae 



3. Antennules 



4. Top of head 



5. First free body seg- 



ments 



6. . Other body seg- 

 ments 



ASELLUS COMMUNIS 



CffiCIDOTEA STYGIA- 



7. Legs 



8. Uropods 



5//'^^r/v responsive; moved the stimula- 

 lated part occasionally 



Strongly responsive; moved the stimu- 

 lated part or crawled 



Strongly responsive; reached for bristle 

 with antennx and gnathopods 



Strongly responsive; moved appendages 

 or crawled 



Stroiglv responsive; less vigorous re- 

 action than when head was touched 



Strongly responsive; less vigorous reac- 

 tion than when head or first seg 

 ment was stimulated, but similar 

 in character 



Fairly responsive; animal often moved 



Strongly responsive; animal crawled 

 (luicklv 



Strongly responsive; \isually moved 

 very quickly 



Extremely responsive; moved backward 

 very quickly 



Strongly responsive; moved backward 

 quickly 



Extremely responsive; with quick and 

 vigorous movements 



Extremely responsive; similar move- 

 ments but less vigorous than 

 produced when head was stimu- 

 lated 



Extremely responsive; with movements 

 like those made when head or first 

 segment was stimulated, but less 

 vigorous 



Strongly responsive; slightly less than 

 when uropods were stimulated 



Strongly responsive; usually crawled 

 quickly 



^This animal had recently undergone ecdysis and consequently was perhaps more than usually 

 sensitive. 



