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S. IKE DA. 



the floor. It is through the movements of the posterior limbs of the 

 female that the frothy mass is kneaded and formed, but the parts moved 

 are confined for the most part to the crus and the pes, the femur remain- 

 ing comparatively still. The movements are not, however, by any 

 means simple. Sometimes the knee and the distal end of the pes being 

 fixed, the ankle-joint is moved backward towards the cloaca, just at the 

 same time that it is flexed. Sometimes the ankle-joint is more or less 

 straightened out and the crus and pes are thrown strongly backwards, 

 the pes of the two sides often crossing each other. Corresponding parts 

 of the two sides move simultaneously. The toes also perform an 

 independent motion of their own ; they are strongly flexed, as if thev were 

 grasping some object. When any one of the motions is begun, it is 

 generally repeated 5 or (j times in succession, for about a minute. A 

 rest of abolît half, a minute follows a series of these motions, before 

 another is begun. 



Let us now see in what relation these motions stand to the produc- 

 tion of the frothy envelope. While these motions are rapidly going on, 

 the eggs together with the jelly-mass are gradually forced out of the 

 cloaca, and are laid down on the bottom of the jar. When the ankle- 

 joints or the crus and pes of both hind limbs are flexed backwards over 

 the newly deposited jelly-mass, the latter easily adheres to the surface of 

 the joints and of the pes, as it is very viscous. When the joints are 

 again moved forwards to their positions on the back of the animal, the 

 jelly adhering to them is pulled out as a thin transparent membrane 

 stretching between the ankle-joints and the proximal part of the pedes of 

 the two sides. When the joints are in the next motion again thrust 

 backwards, the thin membrane is folded downwards and becomes a large 

 vesicle about l j s — L cm. in diameter, as the annexed woodcut shows. 

 The air that forms the vesicle seems to enter from the sides, helped on 

 by the grasping motions of the digits. These large vesicles are formed 

 successively and carried back with each motion of the hind limbs. The 

 large vesicles thus driven back are gradually broken up into smaller 

 and smaller bubbles by the stirring of the crus and pes, when these 



