68 
that is sufficiently intransparent to afford a protection against the 
rays of the sun, and upon the whole to afford a shelter for them." 
Whether the habit of the young Caranx and Gadus merlangus 
to go under Cyanea has anything with the light to do, I do not 
know. It does not appear from the observations hitherto made, 
whether these young fishes go under the jellyfish in dark weather 
as well as in sunshine. Such observations are necessary in order 
to determine whether the object is alone to feed on the jellyfsb, 
as it would be according to Scheuring. 
The suggestion of Doflein mentioned above (p. 59) that the 
transparency of pelagic animals affords a protection against the 
strong light may be recalled in this connection. Both these views 
would appear to support one another. 
Alcock (Op. cit. p. 75) mentions that ,it was usual to find 
shøals of file-fishes hovering round these drift-logs, but with what 
intention we could not discover, for the støomach of one that we 
opened was full, not of barnacles, but of the free-swimming oceanic 
molluscs known as sea-butterflies (Pteropoda)". In my mind there 
is no doubt that also such case is to be explained in the same 
way as above, the fishes seeking shelter under the driftlog against 
the strong light. 
The renewed observations during the present expedition are in 
perfect agreement with this. There is no reason to give a detailed 
account of such observations. I would only mention that once, in 
Panama, I caught some small Rhizosioma's with the young fishes 
following them and put them together into a dish; also here the 
fishes kept following the jellyfish all the time. Here, however, I 
found once on taking up some Salpæ, that a small fish (a species 
of Apogon) was following them, resembling the nucleus of the Salps 
exactly in colour, so it was hardly possible to distinguish it, and it 
was only after capturing them that the fish was seen. This is then, 
evidently, another case of protective resemblance, corresponding 
to the one of the young fishes mimicking the wooden fragments. 
i. Mollusca. 
A very fine instance of mimicry among Molluscs is recorded 
by H.L. Osborn (Op. cit.), viz. the Gastropod Ovulum uniplica- 
tlum which is found on Leptogorgia; the colour of the snails body, 
