218 THE ROYAL SOCIETY OF CANADA 



well as in 9 2, but in 9 1 they were in a single row while those of 9 2 

 were in two or three rows. In Tortanus, Eurytemora and many others 

 the sexes can be separated by the character of p5 in earlier stages. 



Species of Acartia 



During the latter part of July and the first week in August, a 

 species of Acartia was very abundant in the tows taken at the mouth 

 of the St. Croix River opposite the Biological Station. On July 21st, 

 a foggy rainy day, a tow of five minutes was taken off Kitty's Cove 

 when the tide was on the ebb. The copepods were numerous and 

 nearly a pure culture of Acartia of all stages from the nauplius to the 

 adult. The general appearance and specific characters of the adult 

 resembled more closely than any other the description of A. clausi 

 Giesbrecht. The female ranged from 1-08 to 1-13 mm. in length, 

 without any trace of rostral filaments. Some specimens had the lat- 

 eral lobes of the last segment of the forebody beset with from four to 

 six cilia. These cilia were not present in all the copepods examined. 

 Some had them only on the right lobe while others had no trace of 

 them. On the dorsal surface of the first segment of the urosome were 

 a few cilia, but the posterior edges of the first two segments were not 

 clothed dorsally with a transverse row of denticles as in the Nor- 

 wegian material described by Sars. The urosome of the females was 

 half as long as the forebody; the first segment measured -124 mm., 

 the second -072 mm., the third -04 mm., and the caudal furca -072 

 mm. The anterior antennae scarcely exceeded the length of the fore- 

 body, the fifth articulation having a distinct denticle in front. The 

 length of the apical spine of the outer ramus in the second to fourth 

 pairs of legs scarcely exceeded that of the ramus. The p5 were similar 

 to the figure given by Sars. A specimen was obtained holding a 

 spermatophore with the terminal joints of p5 (Fig. 48). 



The male of A. clausi ranged in size from -92 to 1-04 mm. The 

 caudal rami were shorter than those of the female, being about as 

 long as the anal segment. The p5 (Fig. 49) resembled Sars' figure 

 except that the third joint of the left leg had two clumps of cilia on 

 its posterior surface and the terminal joint was more spoon-shaped 

 with the concavity filled with long slender cilia in addition to stout 

 marginal cilia (Fig. 50). The terminal joint of the right p5 had two 

 minute tufts of cilia on its posterior surface (Fig. 51). 



In a tow taken at "Prince" Sta. 1 on July 23rd, 1916, three 

 specimens of Acartia longiremis, two adult females and one adult male, 

 occurred. This is the first record of this species at St. Andrews. It 

 can be distinguished from A . clausi by the lateral lobes of the last 



