TUNICATA. 23 
while the ventral band is absent. In A the ventral band is equal in extent to the 
notochord, and the dorsal extends a little beyond on each side. In B both ventral and 
dorsal bands are about twice the diameter of the notochord. Finally, in C each muscle 
band is about three times the diameter of the notochord, and in some sections I have 
found a slightly greater development of the muscles. In view of these variations, and 
of the fact that the subchordal cells are in some cases in one row, in some in two, or 
even three in a transverse row, I find it difficult to distinguish between Dr. Lohmann’s 
two Antarctic species O. gaussica and O. valdivie. The first-named is described * as 
having “schmaler, die Chorda seitlich kaum tiberragender Muskulatur,” while the 
second has “ Muskulatur breit, etwa 4-mal so breit wie die Chorda” ; but practically 
both these conditions are found in one tail of our specimens, and are shown in fig. 16. 
The histological details of the wall of the notochord, the muscular and epithelial 
layers and the test, with part of a subchordal cell underlying it, are shown in fig. 17. 
OIKOPLEURA Sp. 
There are also about 20 small tubes containing much smaller specimens of 
Oikopleura, which I do not care to refer to a species. Most of them are probably 
young, all are very opaque, and some are shrivelled or mutilated. The only value 
of this record is to show that small forms of Oikopleura do occur, in some cases in 
considerable numbers, at the localities given in the following list :— 
“31. xii, 01; Lat. 61° 12’ 39” S.; Long. 173° 29' 42" E.” (One specimen.) 
“ Winter Quarters, 6. v. 03; No. 4 Hole, 5 fms.” (‘Two specimens.) 
«Winter Quarters, 15. v. 03; No. 8 Hole, 10 fms.” (One specimen.) 
“18. v.03; No. 4 Hole.” (Three specimens.) 
“Winter Quarters, 29. v. 03; No. 4 Hole, 5 fms.” (Eighty specimens.) 
“Winter Quarters, 1. vi. 03; No. 8 Hole, 10 fms.” (Five specimens.) 
«¢ Winter Quarters, 1. vi. 03; No. 8 Hole, 10 fms.” (One specimen.) 
“Winter Quarters, 28. vi. 03; No. 8 Hole, 10 fms.” (Twenty-one 
specimens. ) 
9, “ Winter Quarters, 13. vii. 03; 10 fms.” (Three specimens.) 
10. “24. vii. 03; No. 8 Hole, 10 fms.” (Six specimens.) 
11. “Winter Quarters, 1. viii. 03; No. 8 Hole, 10 fms.” (Seven specimens.) 
12. “ Winter Quarters, 13. viii. 03; No. 8 Hole, 10 fms.” (Three specimens. ) 
13. “ Winter Quarters, 21. viii. 03 ; No. 8 Hole, 10 fms.” (Seventeen specimens.) 
14. “Winter Quarters, 2. xi. 03; No. 12 Hole, 10 fms.” (Three specimens.) 
15. “12. vi. 04; Surface, Lat. 49° 40’ S.; Long. 172° 18’ 30” W.” (140 
specimens. ) 
16. “21. vi. 04; Lat. 56° 12’ 45" 8.3; Lone, 136° 18’ 30” W., 10 fms.” (Fifty 
specimens. ) 
ON DOR we 
* Lohmann, op. cit., p. 859. 
