18 LIVERPOOL BIOLOGICAL SOCIETY. 
mud; so that the varieties of colouring found in the 
Tritoma are suited to the various conditions of the 
Alcyonium colonies. The small branched cerata along the 
back of the T'ritonia aid the protective resemblance not 
only by contributing to the general colouring, but also by 
their similarity in appearance to the crown of tentacles of 
the partially expanded polypes. They are placed at just 
about the right distance apart, and have the necessary 
tufted appearance. 
Then again, Doto coronata when isolated is a very 
conspicuous and highly coloured animal, but we find it at 
Hilbre Island almost invariably creeping on the under 
surfaces of stones on which are large colonies of the 
Zoophyte Clava multicornis, and in that position the Doto 
is not readily seen. The gay appearance of this Nudibranch 
is mainly due to the large and highly coloured cerata, and 
these agree so closely in their general effect with the upper 
ends of the zooids of Clava covered with their numerous 
tentacles and the clusters of sporosacs, that when the Doto 
remains still it is hidden to a very remarkable extent. 
Dendronotus again, with its very large branched cerata 
(evidently a further development of the small processes of 
the body wall seen in Tritonia) and its rich purple-brown 
and yellow markings, is a handsome and most conspicuous 
object, but I have sometimes found it amongst masses of 
brown and yellow Zoophytes and on purplish red seaweeds, 
where it was very completely protected from observation, 
and I did not for several seconds recognise what I was 
looking at. 
Now these are all cases where the colouring is protective, 
and I have no doubt there are many other similar instances 
to be found amongst the Nudibranchiata, but the species 
of Holis appear to be in a different category. They are 
noted for the very brilliant hues of their cerata, and they 
