Protective Resemblance, etc., in Post-Larval Stages of Cajpe Fishes. 207 
by means of which they can remain swimming about slowly or rapidly, or 
even remain perfectly still in mid-water, where they procure their food. 
They are difficult to see, even in a tank in the aquarium, on account of their 
transparency. They are, however, not quite transparent, as there are a 
number of very distinct but small black dots on the body over the brain and 
at the bases of the vertical fins. The significance of these black dots may 
probably be to further disguise the fish, as the outline of the moving body 
is thereby broken, attention l^eing drawn to the specks. 
The leerfish {Lichia amia) is well protected in its adult stage. It has 
strong and sharp teeth, by means of which it can cause great damage amongst 
other fish, such as mullet, on which it lives. It is of a more or less uniform 
colour, without any apparent modification for concealment. The young, 
however, have a well-marked colour pattern, so distinct from the adult 
condition that they have been described under a different name (Porthtneus 
argenteus) . Various stages of these fish from an inch or two in length to 
about 8 inches show^ the gradual transition to the adult form. The colour 
pattern in the young is irregular but well marked, and consists of dark 
patches and streaks on the body, which is of a greenish colour, the extremi- 
ties of the dorsal and anal fin being brilliant orange. It cannot very well 
be regarded as a striking case of protective resemblance, though doubtless 
it serves to render the body less conspicuous in the shallow and confined 
waters in which these young stages are found. 
The transformation in the colour markings of Lichia, amia are well known, 
and are readily observed in the nettings for fish in estuarine rivers in South 
Africa. Another instance of such a change is not so well known. It was 
recently found in the case of a dogfish (Acanthias, sp. n. ?). In the adult 
there is a series of relatively small white spots along each side of the body, 
but in the young the colour pattern is entirely different. There is a broad 
band of white colour running along each side of the body. It is not exactly 
similar in all specimens, and is interrupted at irregular intervals. Isolated 
white spots occur on the head and above the gill openings ; there is a pair in 
front of the first dorsal and another in front of the second. These pairs are 
constant. The margins of all the fins, including the upper and under side 
of the caudal fin, are also marked out in conspicuous white patches. There 
is no doubt that these are the young of the dogfish referred to, as they have 
frequently been found in the oviduct of this fish. 
The young of the stockfish {Merluccius cajpensis) has also a well-marked 
colour pattern, absent in the adult. 
Other means besides that of resemblance to surroundings are found 
amongst post-larval stages of fishes for their effective protection. Thus the 
post-larval snoek (so well armed, in its adult stage, by its formidable teeth) 
is protected by well- developed serrated spines on the fins and large spines 
on the head. 
