312 
PACIFIC SCIENCE, VoL VIII, July, 1954 
proves to be a useful difference, Ihle may have 
examined some specimens of R. picteti agg.), 
whereas in R. amboinensis it projects only 
slightly and is not independent of the re- 
mainder of the test. 
4. The posterior end projection of R. am- 
boinensis IS large and club-shaped, whereas that 
of jR. picteti is small and almost filiform. 
5. The anterior end projection is short and 
blunt in R. amboinensis, whereas it is moder- 
ately long and filiform in R. picteti. Thus, if 
these last three differences are universal, these 
species deviate somewhat from the usual con- 
dition in salps in that the test is soft (but 
permanent structures are apparently present) 
and yet is useful in species distinction. 
6. The endostyle extends further posteriorly 
in R. picteti than in R. amboinensis. 
Both specimens of R. picteti contained em- 
bryos recognizable as this species, but the 
gut was not yet extended (Eig. 19^). No 
specimens of R. amboinensis contained em- 
bryos old enough to show structures nearing 
adult condition. The largest of these latter 
embryos (length, 0.3 mm.) contained nine 
recognizable body muscles, each of which, 
however, was widely interrupted dorsally and 
ventrally. A study of a nearly mature embryo 
from an aggregate R. amboinensis is thus 
desirable. 
Genus Metcalfina Ihle and 
Ihle-Landenberg, 1933 
Solitary form with 10-13 asymmetric, ven- 
trally interrupted body muscles; these are all 
joined dorsally. Aggregate form with six ven- 
trally interrupted body muscles, of which M 
V and VI are independent from other body 
muscles. Test of both forms is firm and bears 
serrated ridges. 
One species, Metcalfina hexagona. 
Metcalfina hexagona 
(Quoy and Gaimard) 1824 
Eigs. 2Qa-d, 21a-d 
Salpa hexagona Quoy and Gaimard, 1824: 505; 
Bomford, 1913: 244; Oka, 1915: 30. 
Salpa triangularis [?] Quoy and Gaimard^ 
1824: 511. 
Salpa biensis [?] Blainville, 1827: 123. 
Salpa lineata [?] Lesson, 1830: 268. 
Salpa monotoma [.^] Quoy and Gaimard, 1834: 
59T 
Fig. 20. Metcalfina hexagona, solitary form, a. Whole animal, dorsal aspect; h, test, left side; c, test, ventral 
surface; d, schematic cross section of test at level of ganglion. 
