. 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.

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