MARINE BIOLOGICAL STATION AT PORT ERIN. 187 



suronier, specimens from Port Erin examined last August 

 proving to be as completely so as the large 'Laminarian 

 worms ' were at Blackpool from the end of January to 

 the middle of May. Meanwhile, Mr. Gamble would be 

 very greatly obliged if his fellow workers, during the 

 coming spring, could send to Owens College, Manchester, 

 any specimens of what are suspected to be larvae or post- 

 larval stages of the common lug-worm, the eggs and 

 development of which are still quite unknown." 



Amongst the workers at the Biological Station at 

 Easter was Dr. C. H. Hurst, of Dublin. Dr. Hurst 

 kindly offered to do some work for me, so I suggested that 

 he should make a series of observations and experiments 

 in regard to the currents of water entering and leaving 

 the two apertures of Polycarpa glomerata, a gregarious 

 red-coloured simple Ascidian found in great abundance 

 under the limestone masses at Perwick Bay, and clothing 

 the sides of the caves at the sugar-loaf rock. Dr. Hurst 

 has sent me the following account of his results along 

 with some diagrams and an exact record of all his 

 experiments : — 



" At the request of Prof. Herdman, I made some simple 

 experiments at the Port Erin Laboratory of the Liverpool 

 Biological Committee, at Easter, 1897, with the object of 

 discovering whether or not the direction of flow into and 

 out of the branchial and atrial cavities of Polycarpa was 

 constant. 



" To test the direction of the currents, the water in the 

 immediate neighbourhood of the branchial and atrial 

 apertures was made streaky by causing small vortex rings 

 of water-colour paint (lamp black) to pass close to these 

 apertures. This was easily effected by means of a small 

 glass cannula with an india-rubber cap. To eliminate 

 the effect of gravitation, the paint was mixed in the first 



