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TRITONIA PLEBEIA.
Dr. Johnston now considers his Tritonia ymlchra to be a variety of this, which is not
improbable, considering how much the species varies in colour, though we have not seen a
specimen entirely agreeing with his description. We have more than once met with a lemon-
yellow variety, which may possibly be the Doris elecfrica of Pennant, his figure agreeing
better with the form of this species than of any other we are acquainted, with.
Tritonia plebeia is not by any means an active animal. It is very generally distributed
in the British seas, and is one of the commonest deep-water nudibranchs of our eastern
coast. Professor E. Forbes found it in the Ægean, but it has not yet been noticed on the
western shores of Europe. Probably it may have been overlooked, from its similarity to the
young of the larger species.
We have not often met with the spawn of this species. It is usually deposited on the
stems of corallines, and forms an irregular waved or festoqned mass, the spiral nature of
which it is not easy to trace. When deposited on a flat surface, however, it assumés a
regular waved .spiral, as we had the opportunity of seeing in an individual that spawned on
the side of a glass. The gelatinous thread is narrow and rounded, containing numerous
eggs, arranged aboilt five abreast throughout. This individual spawned in October, but
we have also met with thé spawn in May.
Figs. 1, 2, 3. Tritonia plebeia, in different positions.
4. A branchial plume more highly magnified.
5. A tentacle very highly magnified.
6. Spawn.
7. A portion of the same highly magnified.