338 MR. E. E. unwin: notes upon the 



she walks as well ; but if he is moving rapidly, she allows herself to be 

 dragged alone. In this case she bends her head and fore-part of the thorax 

 downwards so as to present her rounded back to the rush of water and to 

 the obstacles that may be in the way. When the male stops she lifts her 

 head and continues her feeding and breathing actions. The male is not 

 inconvenienced by the presence of the female, as his larger size enables 

 him to reach forward in front of the female for food. 



If a male and female are put together in a dish of water, the process of 

 capture and hooking can be easily watched. When they meet, the male 

 quickly seizes the female ; sometimes he has a long chase before he can 

 secure her. Kaulbersz gives some observations, noting that if several males 

 are present there are fights for the female, and that yellow-coloured males 

 usually come out victorious. The female is secured by the 1st pair of legs, 

 which are prehensile. In the male these legs are especially large and 

 powerful (PI. 25. fig. 2). The figure shows the modification. The propodite 

 is much enlarged, forming one side of the claw, and containing the powerful 

 muscles for working the dactylopodite down upon it. Both of the segments 

 have the opposable faces roughened with spines, and, in addition, there is a 

 process carrying a few large spines near the proximal end of the propodite. 

 The carpopodite is very much reduced. 



When the male grasps the female, he turns her quickly over, as though 

 inspecting her condition. If she has been impregnated already, or has the 

 brood-pouch developed, lie releases her at once ; if she is in the right 

 condition, he quickly turns her about until he can hook his 4th pair of legs 

 over the edges of her thorax. I do not find that he prefers to lie on his 

 right side as Kaulbersz suggests ; indeed, he more often lies on his back 

 so as to bring all his legs into nse. Having secured the female, the male 

 rights himself and walks off with the female slung beneath. 



The real meaning; of this association of male and female has become clear 

 by a number of observations made in the spring of 1908 and verified several 

 times since. Most observers refer to this association and to the varying 

 times of its duration : but they have not appreciated the real significance of 

 it or the reason for the longer or shorter time of association in this marriage- 

 clasp. 



The length of the period of association depends upon the nearness of the 

 next female ecdysis. Impregnation and egg-laying cannot take place until 

 a change of cuticle releases the large oostegites for the brood-pouch and 

 exposes the external openings of the oviduct. It is the casting of the hind- 

 half of the female cuticle which gives the signal for the attentions of the 

 male, and this casting is always accomplished before copulation. If one 

 thinks of the short time which elapses between the casting of the cuticle and 

 egg-laying, as well as the delicate coudition of the creature at the time, it 



