TUNIC ATA. 23 



while the ventral band is absent. In A the ventral baud 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 0. gaussica and 0. valdivise. The first-named is described * as 

 having " schmaler, die Chorda seitlich kaum iiberragender 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. 



OlKOPLEURA 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 : 



1. " 31. xii. 01 ; Lat. 61 12' 39" S. ; Long. 173 29' 42" E." (One specimen.) 



2. "Winter Quarters, 6. v. 03 ; No. 4 Hole, 5 fms." (Two specimens.) 



3. "Winter Quarters, 15. v. 03; No. 8 Hole, 10 fms." (One specimen.) 



4. " 18. v. 03 ; No. 4 Hole." (Three specimens.) 



5. "Winter Quarters, 29. v. 03 ; No. 4 Hole, 5 fins." (Eighty specimens.) 



6. "Winter Quarters, 1. vi. 03 ; No. 8 Hole, 10 fms." (Five specimens.) 



7. "Winter Quarters, 1. vi. 03; No. 8 Hole, 10 fms." (One specimen.) 



8. "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.) 



1C. " 21. vi. 04 ; Lat. 5G 12' 45" S. ; Long. 136 18' 30" W., 10 fms." (Fifty 

 specimens.) 



* Lohuiaiin, op. cit., p. 359. 



