The Recognition of Sex 223 



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ited by the male on the ventral side of the thorax of 

 his mate. After the eggs are fertilized the male 

 continues to swim about with the female as before. 

 "The instinct of the male amphipod ^ to seize and 

 retain hold of the female is one of remarkable 

 strength. The male retains his hold, despite all 

 efforts to dislodge him, with remarkable persistence, 

 and will still ding to the female after the posterior 

 half of his body has been cut away. My own obser- 

 vations on the sexual behavior of amphipods relate 

 mainly to three species, Amphithce longimana Smith, 

 Hyalella dentata Smith, and Gammarus fasciatus 

 Say. The sexual behavior of these three species is 

 remarkably similar although they belong to as many 

 distinct families. The female while carried about 

 keeps remarkably impassive. Her thoracic legs are 

 drawn up, the abdomen held strongly flexed, the 

 whole body assuming as compact a form as possible. 

 She takes no part in swimming; the movement of the 

 pleopods when the body is strongly bent upon itself 

 serves only to keep a current of water passing by the 

 gills. She is carried about like a helpless burden, 

 allowing her vigorous spouse to assume the entire 

 labor of transportation and the responsibility for 

 keeping her as well as himself out of danger. 



"The efforts of the male to seize the female and 

 get her into the proper position to be carried have 

 the effect of inducing her to throw herself into the 



^ Quoted from an article by the writer on "Sex Recognition 

 in Amphipods," published in the Biological Bulletin, Vol. 5, p. 

 288, 1903. 



