SYSTEMATIC REPORT 85 



St. 677. 27/8. iv. 31 (night). North-west of Tristan da Cunha, 420-0 m., 5 adult cJcJ, 7-8 mm., 4 adult $?, 5-6 mm. 



(2 ovig.), 1 damaged ovig. $, 5 mm. 

 St. 679. 29. iv. 31 (day). South-east of Rio de Janeiro, 2 hauls: (i) 300-0 m. (night), 2 adult <$<$, larger 11 mm., 



1 imm. $. ; (ii) 500-250 m., 1 ovig. $, 4-5 mm. 

 St. 685. 3. v. 31 (night). East of Pernambuco, 350-0 m., 8 adult <J^, largest 7-5 mm. 

 St. 689. 6. v. 31 (night). East of Pernambuco, 410-0 m., 5 adult (Jo*, largest 7-4 mm., 4 juv. SS\ 3 adult $$, largest 



6-2 mm., 2 juv. $$. 

 St. 694. 10. v. 31 (night). Mid-Atlantic, north-west of St Paul's Rocks, 210-0 m., 1 juv. (J, 3-5 mm. 

 St. 695. 11. v. 31 (night). South-south-west of Cape Verde Is., 370-0 m., 10 adult $$, largest 7-2 mm., 1 juv. <J; 



1 adult $, 5 mm., 3 juv. $$. 

 St. 697. 12. v. 31 (night). South-west of Cape Verde Is., 460-0 m., 1 adult <J, 8-5 mm. 

 St. 698. 13. v. 31 (night). South-west of Cape Verde Is., 470-0 m., 3 adult cJ<J, largest 9 mm., 2 adult 9$, with 



empty brood sacs, 7-5 mm. 

 St. 699. 14. v. 31 (night). West-south-west of Cape Verde Is., 370-0 m., 1 adult $, 11-2 mm. 

 St. 700. 18. v. 31 (day). North-east of Cape Verde Is., 2025-0 m., 2 o*6*» IO mm., 1 $ adult, 6 mm. 

 St. 703. 18. x. 31 (night). South-south-west of Cape Verde Is., 358-0 m., 1 adult <J, 11 mm. 

 St. 704. 19. x. 31 (night). South-west of Cape Verde Is., 231-0 m., 7 imm. S3, largest 6-4 mm., 6 adult $$ 



(1 ovig.), 5-5-6-8 mm., 1 small juv. $. 

 St. 705. 20. x. 31 (night). On equator north-east of Pernambuco, 150-0 m., 1 adult ?, 7 mm. 

 St. 706. 21. x. 31 (night). North-east of Pernambuco, 354-0 m., 1 adult $ with large empty brood sac, 7 mm. 

 St. 709. 24. x. 31 (night). Off Abrolhos Is., 216-0 m., 1 adult <J, 5-5 mm. 

 St. 713. 29. x. 31 (night). East of Porto Alegra, 200-0 m., 1 imm. ?, 5 mm. 

 St. 1371. 19. v. 34 (night). South-east of Port Elizabeth, South Africa, 146-0 m., 13 adult $$, largest 11 mm., 



4 juv. (J (J, 13 adult $$ (7 ovig.), largest 9 mm., 6 juv. $$, smallest ovig. $, 5 mm. ; $$ of 7 mm. quite immature. 

 St. 1372. 20. v. 34 (night). East of East London, South Africa, 102-0 m., 2 adult cJc?. 10 mm., 1 adult $, ovig., 



8-5 mm., 1 juv. $. 

 St. 1567. to. iv. 35 (night). North of Prince Edward I., 1350-0 m., 4 adult $9 with large empty brood sacs, 



io-io-2 mm. 

 St. 1571. 21. iv. 35 (night). Midway between Durban and the south of Madagascar, 500-0 m., 1 adult 9, 7-5 mm., 



1 juv. $. 

 St. 1602. 27. x. 35 (night). West of Cape Frio, 175-0 m., 1 adult <J, 11-5 mm. 

 St. 2042. 22. iv. 37 (day). On meridian o° of Greenwich due west of Saldanha Bay, South Africa, 0-5 m., 1 adult ?, 



5 mm. 



St. 2044. 23. iv. 37 (day). Due west of Orange River estuary, 0-5 m., 1 adult $, 5-5 mm., 1 juv. $. 



St. WS 133 'T\ 14/15. vi. 27 (night). Midway between Gough Is. and Cape Town, 0-5 m., 1 adult <J, 11-5 mm. 



Remarks. The species of the genus Siriella present great difficulties to the systematist, because in 

 most of them growth and, with growth, changes in form, continue long after sexual maturity has 

 been reached. As a result, individuals may be fully adult and yet show considerable variation from the 

 published description of the species. In his report on the Challenger Schizopods G. O. Sars (1885 a, 

 p. 205) commented on the variations in size among the specimens of S. thompsonii, but he did not 

 record any differences correlated with size in the armature of the telson and uropods. In the Dis- 

 covery material also there is great variation in the size of adult individuals. Ovigerous females of 

 4-5-5 mm. are common, but they may be as much as 10 mm. in length. It appears that the males 

 attain a greater length than the females before they become sexually mature. Only once (station 709) 

 did I find a male of 5-5 mm. which seemed to be sexually mature with well-developed hirsute lobes 

 on the antennules. For the most part males of 7 mm. were obviously immature. 



In juveniles and small adults the number of spines arming the outer margin of the exopod of the 

 uropod varies from one to three, in larger animals there may be four, with the beginnings of a fifth, 

 and only in the largest specimens are there six to seven as described in the types. This variation is 

 obviously due to growth changes. 



