144 N. AnnaNDALE : The Fauna of Brackish Ponds. [VOL. I, 1907.] 



I did not find, however, that individuals of either brood lived for 

 more than a few days in my aquarium, although they fed readily. 

 Judging from the succession of broods in the pond, the life of the 

 medusa, as might be expected, is short ; while the hydroid probably 

 does not survive for more than one cold season. 



The medusae are sluggish in their movements. As a rtde they 

 do not swim at the surface but rise up to it occasionally by a rapid 

 succession of pulsations, and then sink again with the dorsal surface 

 of the umbrella downwards. On reaching the bottom they gene- 

 rally lie still for a few minutes and then rise obliquely sufficiently 

 high to right themselves. When this has been effected, they often 

 make another ascent to the surface, and the manoeuvre may be 

 carried out several times in succession. While they are sinking, the 

 velum remains expanded and the tentacles maintain their position 

 parallel to the longitudinal axis of the bell, except when they be- 

 come entangled together. The manubrium is, however, in almost 

 constant motion, twisting in all directions and apparently remov- 

 ing microscopic particles from the tentacles and the ventral surface 

 of the velum. Occasionally the medusae move through the water 

 obliquely for a short distance by a regular series of slow pulsa- 

 tions, and more frequently they float along just above the bottom, 

 on which the tentacles and manubrium trail, in an upright position. 



Although the tentacles may be used in retaining microscopic 

 organisms, which the manubrium removes from them, larger prey 

 is captured directly by the mouth, which picks it up from the bottom. 

 I have on several occasions observed young examples of the small 

 univalve mollusc Bithinella cmiingensis, Preston, which is enor- 

 mously abundant in the ponds, being seized in this way. A long 

 struggle always ensued before the medusa was able to detach and 

 lift the prey, which, however, was finally taken into the stomach, 

 distending it greatly. The empty shell was ejected after a few 

 hours. Another method of feeding was also observed, in this case 

 on a filamentous alga. The medusa attached itself by its mouth 

 to a filament of the alga and sucked out the contents, its stomach 

 becoming perceptibly green in the process, which lasted for some 

 hours. 



These observations were of course made on captive specimens, 

 but there is no reason to think that the actions recorded were in any 

 way abnormal; so little is known about the movements and feed- 

 ing of medusae that any notes of the kind have considerable interest. 

 I could not detect evidence of either negative or positive heliotrop- 

 ism in the medusae, but their powers of progression are so feeble 

 that perhaps this was hardly to be expected. Their position in the 

 pond appeared to be due entirely to the direction of the wind ; if 

 there was no wind, they remained close to the plants of Nats on 

 which the hydroid was growing, and on which Bithinella was very 

 abundant. 



