BEHAVIOR OF LOWER INVERTEBRATES 397 



and sometimes the females wage ineffectual conflicts with one 

 another. Although the males may perform various antics before 

 the females during the breeding season, Pearse found no con- 

 vincing evidence of the occurrence of sexual selection. 



Polimanti (35) finds that many crabs feign death in various 

 positions and assume various attitudes. The species that are 

 habitually exposed show the response in a more pronounced 

 form than species that bury in the sand or live symbiotically 

 with sponges. The duration of the feint depends upon a variety 

 ot external stimuli, but is little influenced by the substratum, 

 light, or visual stimulation of passing objects. The death feint 

 is not a voluntary reaction nor a manifestation of hypnosis, but 

 a special "tonic reflex." 



Rynberk (36) in a general review of the subject of the seg- 

 mental tunctions of the nervous system gives an account of the 

 analysis of many of the instincts of the lower invertebrates. 



In Stenophora juli Sokolow (37) finds that progressive move- 

 ments are caused not by a contraction of myonemes, but thiough 

 the secretion ot gelatinous threads at the posterior end of the 

 body. In acid media which dissolve these threads there is no 

 progressive locomotion, although other movements of the body 

 occur for which the myonemes are responsible. The rate of 

 movement increases with temperature up to an optimum of 

 28 to 29 C, with maximum at 49 to 42 C, minimum at 

 4° to 5 C. 



Vieweger (38) has made a detailed study of chemo taxis in 

 Paramecium and Colpidium, treating especially of the influence 

 of various combinations of chemicals upon the diffeient trop- 

 isms of the animals. 



Weymouth and Richardson (39) find that the food of Emerita 

 analoga, the common sand mole of the sandy beaches of western 

 North America, consists of microscopic organisms, strained from 

 the water by means of the highly modified antennae which are 

 furnished with numerous fine hairs. As the waves retire from 

 the beach the Emeritas thiust out their antennae from the 

 sand, and then draw them back again when the water has 

 drained off; then they fold in the antennae, which deliver the 

 food to the mouth parts, which are highly modified to deal with 

 the catch ot microscopic forms. The sand moles are well adapted 

 by the form of the body and the character of the appendages for 



