28 TRANSACTION S LIVERPOOL BIOLOGICAL SOCIETY. 



" Some of the above were collected by Miss M. 

 Kni<i-ht, B.Sc, and Miss H. Coburn, B.Sc, at Peel 

 duriuc tlie Summer vacation." 



During July and August Dr. H. E. Eoaf investi- 

 gated the eifect of the concentration of oxygen and free 

 carbon dioxide on the rhythmical movements of marine 

 organisms. He writes as follows: — " The object was to 

 find out if these movements, like those of mammalian 

 respiration, were mainly influenced by the partial 

 pressure of carbon dioxide and not appreciably affected 

 by the concentration of oxygen. In the event of carbon 

 dioxide exercising the main influence, it was further 

 desirable to discover if this effect were due to an increase 

 of acidity or to the increased partial pressure of carbon 

 dioxide. The experiments were carried out by measuring 

 the rate of the rhythmical movements of rock barnacles 

 (^BaJrnius halanoides) and the rate of the gill movements 

 of a small fish [Coitus scorpins) under dilferent 

 conditions. The results for barnacles suggest that the 

 lower the oxygen concentration the slower are the move- 

 ments, and with carbon dioxide increasing concentration 

 makes the movements more sluggish. With the fish the 

 reverse holds, namely, that the low concentrations of 

 oxygen and high concentrations of carbon dioxide both 

 increase the rate of movement. The influence of oxygen, 

 liowever, is so slight that it approaches tlie limit of 

 experimental error. In both cases the action of carbon 

 dioxide was due to the increase of acidity (hydrogen ion) 

 with increased concentration of carbon dioxide. It is 

 hoped io publisli full details of this investigation and iis 

 results in a short time." 



Dr. Tattersall, of Manchester University, reports: — 



" During the Easter vacation I spent a fortnight at 



the Port Erin liiological Station, in a furtlier attempt to 



