On the forest floor, there was little litter but a lot of 
saplings of the forest trees* This meant that the forest was 
actually regenerating. 
REFERENCES 
I.U.C.N. : First Draft of a V/orld Conservation Strategy. 
Dale, I. & Creenway, P.J. Kenya T rees and Shrubs . 
*I.U.C.N. - International Union for the Conservation of Nature 
and Natural Resources. 
P.W. Mumiukha, lecturer, Egerton College, Njoro, Kenya 
SOCIETY LECTURE NOTES 
On 10th September 1979 Dr Ken Book lectured to the Society on 
the fishes of the coral reef, concentrating on their colouration, 
schooling habits and economic habits. 
The startling colours of coral fishes are due to the effects 
of two specialised cells - chromat ophores containing melanin and/ 
or carotenoids, and iridocytes containing the purine guanine which 
produces iridescence. Meleinins alone produce dark browns or blacks, 
mixed ^with carotenoids they give a range of blues and greens; 
carotenoids alone produce reds, yellows and oranges. The colours 
and patterns also depend on whether the pigment is widely dispersed 
or concentrated in one spot in the pigment cells. The degree of 
dispersion is largely under nervous control though in amphibians 
it is mainly controlled by hormones* 
Colouration in fishes serves the same function as in other 
animals though, as always, it is important to realise that colour 
only plays an important part in the lives of 'animals having receptors 
able to respond to light of different wavelengths. As 20 to 30 
species, many of them congeneric, may be living together in- close 
proximity one important function of colouration i^i coral fishes 
is to provide distinctive sign stimuli which play a major role in 
preventing interspecific matings e Forme with poisonous flesh or 
venomous spines often have warning colouration and, as among insects, 
these forms may have harmless mimics. On the other hand, some 
dangerous forms are among the most cryptic of all fishes, the stone- 
fish being a classic example. Red fishes which out of water do not 
appear cryptic are usually nocturnal and are most difficult to see 
when swimming at night* 
Dr Bock then went on to discuss schooling. This is an extremely 
widespread habit among fishes, sometimes occuring throughout the 
life of the fish but more often being characteristic of either 
adults or juveniles. Juvenile schooling is generally commoner 
than adult schooling, about half of all fish species school as 
juveniles and about a quarter as adults. Schools are called non— 
138 
