NATURAL HISTORY SOCIETY OF GLASGOW. 61 



Immediately on stopping the current is reversed, beginning again 

 slowly, as if with an effort, then gradually increasing in rapidity. 

 In this way the circulation is carried on, first in one direction, the 

 blood flowing in one set of vessels, then stopping, and returning 

 in the same; and so, now backward, now forward, every two 

 minutes the flow of the current is reversed. Apparently the effort 

 required to propel it towards the rectal side was much less than 

 that required to' propel it back; still the time occupied by the 

 seventy pulsations was about the same in either direction. 



Within dead bivalves, Ascidia intestinalis is usually found, 

 apparently protected thereby, as it retreats within them whenever 

 touched. Though at first sight appearing only about an inch in 

 length, it will elongate about three or four times as much when 

 fully distended and lying stretched out with its orifices open. 

 In this species the number of pulsations before the current is 

 stopped is far more numerous than in the preceding. 



With the towing-net we once obtained what appeared to be 

 Appendicularia flagellum, if this species is not probably the tadpole- 

 larva of some other ascidian. It was in every respect very similar 

 in appearance, though considerably larger than the larva in the 

 ovum, and propelled itself by a wriggling motion of the tail, very 

 like an ordinary tadpole. 



Dredging opposite the Bogany Farm and towards the Point, an 

 extensive meadow of Zostera marina is crossed, the feeding-ground 

 of numberless Asteriadce, Buccina, and other mollusca, but more 

 especially of the Brittle-stars. Here the dredge has frequently 

 come up with the bag stuffed full of them, and with nothing else, 

 just as if they had been gathered by some mermaid's fingers. 

 Three species, Ophiocoma granulata, 0. hellis, 0. rosula, will be found 

 — the first in greatest abundance. Solaster papiposa is occasionally 

 met with; and the common star-fish, Uraster ruhens, is everywhere 

 abundant. On the fishing-ground opposite the Catholic Church, 

 beyond Ardbeg Point, very large Urasters have come up, and also 

 the Luidia fragillissima. Two specimens of the latter had respec- 

 tively seven rays ; in one the rays were seven inches in length, in 

 the other nine inches; and the breadth, from where it came off 

 from the disc or central part of the body, was one and a-half 

 inches ; the length across, from the tip of one ray to the tip of the 

 opposite, being nineteen inches. 



