238 



E. W. SEXTON. 



left standing for some time ; as the water becomes foul the animals 

 crawl out of the crevices and holes in which they have been hidden. 



The males are very active. Mr. Clark, the naturalist on board the 

 Oithona, says of the Eddystone specimen that when caught it darted 

 about from side to side with quick jerky movements. This specimen is 

 the largest male yet recorded, measuring 10 mm. from the tip of the 

 rostrum to the tip of the telson. Of the three other males caught at 

 Plymouth, one taken off Drake's Island measured 8 mm. ; the other 

 two recorded by Garstang {Mar. Biol. Journ., Vol. II, p. 123) were 

 4 mm. and 5 mm. long and had 9 and 12 joints respectively in the flagel- 



Anthura gracilis. Fit;. 2. — IVlson, 2, x 42. 

 Cyathura carinntn. Fig. 3. — Telson, $, x 42. 



o, muscle attachment ; h, muscle attachment, inner uropod ; 



st, statocyst. 



lum of the upper antenna. A suggestion has been made that the male 

 on reaching sexual maturity has an active but short life. I think the 

 note just referred to helps to solve this question. These two small males 

 had already reached sexual maturity, as shown by the development 

 of the sensory setse of the upper antennae (a secondary sexual character 

 appearing at maturity), but that they were not nearly full grown can 

 be seen on comparison with the Eddystone specimen. The number of 

 joints in the flagella increases with age. The Eddystone specimen — 10 

 mm. in length — had 20 joints developed in the flagellum of the upper 

 antenna, thus showing that the period of sexual maturity and activity 

 had extended over a length of time sufficient to allow for several moults 

 and the consequent considerable increase in growth. 



