DESCRIPTION OF SPECIES 63 



These do not seem to be entirely satisfactory distinctions, and the difficulty arises from the in- 

 complete description of T. propinquum given by Herdman (1886). Arnback, however, was convinced 

 that the two species are distinct, and there is no doubt that the 'Discovery' specimen belongs to 

 T. auriculatum. 



Distribution. Subantarctic (Strait of Magellan; Guaitecas Islands, Chile; Falkland Islands). 



1.0 mm 



0.2 mm 



Text-fig. 14. Trididemnum auriculatum Michaelsen (St. WS 84): A, zooid; B, larva. 



There are also in the collections several colonies of didemnid ascidians which I am unable to place, 

 even in their correct genus, because the zooids have no gonads. It would be very unwise to try to 

 name these specimens using other characters, because with few exceptions the nature of the testis 

 and sperm duct is almost essential for the determination of genera and species in this family. 



