Thompson — Fauna and Flora of Valencia Harbour, Ireland. 737 



III. — Eepokt on the Fkee-Swimming Copepoda (1895-98). 

 By Isaac C. Thompson, F.L.S. 



The collection of material from which this Eeport is compiled consisted 

 of ninety-six hottles of Plankton taken by surface tow-net on ninety- 

 six separate days during the years 1895 to 1898, by the Misses Delap, 

 of Valencia Island, and by Mr. E. T. Browne, of University CoUege, 

 London. During the summer of 1896, Mr. Browne had as companions 

 Mr. A. 0. Walker, p.l.s., of Colwyn Bay, and Mr. E. W. Gamble, of 

 Owens College, Manchester. Both of these gentlemen have kindly 

 sent me material they collected by tow-net, and it is included in the 

 present Eeport. 



All the material collected for examination was immediately pre- 

 served in formalin . A 5 per cent, solution appears to be the strength 

 best suited for these delicate Crustaceans, and is probably as efficient a 

 preservative as is known. 



The free-swimming Copepoda of our coasts vary in size from 1 mm. 

 to 4 mm. in length. The mode of examination which I have found 

 the best and quickest is as follows : — After carefully shaking the 

 material in the bottle, a quantity is poiu'ed into a shallow open glass 

 plate about 4 inches long, 2 inches wide, and i inch deep. Such a 

 plate (which I have been able to obtain only from Messrs. Cogit & 

 Co., Paris) is curved inside like a watch-glass, and the contents can be 

 rapidly gone over by means of a strong lens, or a simple dissecting 

 microscope, or still better on the large flat stage of a Swift's Stephen- 

 son binocular microscope, using a 2-inch objective. Every portion is 

 thus systematically examined ; and those animals identified or required 

 for further examination are easily picked out with a veiy fine needle, 

 or better with the lower part of a cat's whisker cut flat at the end and 

 mounted. 



The collection includes in all thirty-seven species, the majority of 

 which are entirely free -swimmers. The others are all flesh-feeders, 

 living mostly in tidal pools and shallow water. Many of the latter 

 are very small, and it is probable that their number might have been 

 considerably increased had a net of smaller mesh been employed, as 

 many species would doubtless pass through the 50 to the inch mesh, 

 which was the one rmiformly used. 



