polarised when they are rather loose and ‘untidy* and polarised 
when all individuals are lined up in the same direction, are evenly 
spaced, move at the same speed and malce well synchronised turns. 
Schooling appears to he an adaptation for life in sub-optimal 
habitats, especially in open water where there is a patchy food 
supply* Individual fishes are less likely to be taken by predators 
due to what is called the ^confusion effect*. The chances of any 
one individual being taken also decreases as school size increases 
in much the same way that simultaneous calving by wilderbeest reduces 
the chances of any one calf being taken by hyaenas and other predat- 
ors. 
Br Bock finally explained why the East African coast is never 
likely to become a major fishing ground. The worlds* major fishing 
grounds are located on continental shelves with relatively smooth 
sandy or muddy surfaces which permit trawling. The East African 
Coast lacks a continental shelf free of snags - any attempt to 
trawl over coral reefs would rip nets to pieces. Nonetheless 
substantial numbers of fish are caught by tidal stake traps, dema 
traps and hand lines, providing , both high class protein and useful 
income for the coastal people, 
Br Bock’s interesting talk was accompanied by some excellent 
slides, taken by a number of his friends (he not being a photog- 
rapher) which clearly illustrated most of the points he discussed. 
J.E.R* 
BELOSPERMA QEHLERI: AN INTERESTING REBISCOVERY 
Mesembry^i^ themum oehleri v/as described by Engler in 1909 from 
a specimen collected by Oehler and Jaeger on 8th January 190? north 
of Lamuniane in the Ndassekera Mountains in northern Tanzania. 
Since then it has not been found again. till photographed early 
this year by Mr Peter Bavey on a. quartzitic hill at 1,950 m in 
Narok Bistrict, The colour of the petals (really staminodes), 
which was not recorded by the first. collectors and is therefore 
not stated in the description of this species in the P^l^o^ra ^ 
Tropical East Af rica Aizoac eae (l96l ), is magenta* 
. ■ J • B * G- . 
FOR SALE 
JOHN HANNING SPEKE, The Journal of the Biscovery of the Source of 
the Nile, 1863, 1st Edition* She 1,000.00 or nearest offer. 
Please contact the Secretary, P.O. Box 44486, NAIROBI 
Toyota Landcruiser 1972 MWB Hardtop, well maintained and reliable. 
Knows the way to the best places in Kenya. Telephone Bishop 557811 
(office) 520152 (house). 
139 
