SUNIER: Marine fish-ponds of Batavia. 231 
the lateral, and concavity towards the median side. These two crescent- 
shaped patches are parts of the exomeninx gleaming through the skin 
and through the dorsal investing-bones of the skull; they contain besides 
chromatophores also iridocytes, thus differing from the part of the 
exomeninx between the patches which contains chromatophores only. 
Moreover the skin over the crescent-shaped patches holds fewer chromato- 
phores than the skin between them. 
In the kepala timah the action of the chromatophores obscuring the 
white little spot may be observed in the following manner. A live kepala 
timah is taken out of the water and is placed between a pair of glass or 
metal blocks in a little glass dish without water under a binocular micros- . 
cope. Studying the spot for instance through the pair of objectives (as) 
and the Huygens’ oculars no. 3 of Zeiss, we see through the skin and the 
investing bones of the skull that the spot is covered with a dark haze from 
the expanded chromatophores. Next water is poured into the dish and the 
dark haze lifts after which the chromatophores are seen lying in the shape 
of very small contracted circular dots af the upper surface of the white spot. 
We must now stop for a moment to discuss the colouring of the fins. 
It is chiefly by these colours that with the kepala timah one can distinguish 
the males from the females. This difference is not mentioned in the sys- 
tematic literature available here: BLEEKER (4), DAY (7) and GÜNTHER (5). It 
is however well-known that with Cyprinodontidae the males are generally 
more beautifully coloured than the females. 
The kepala timah has the free distal edge of its anal fin coloured a 
more or less clear red. This red passes proximally into yellow. Under the 
microscope it is evident, as might be expected, that these colours depend 
upon the presence of lipochrome-chromatophores. Parallel to the red-yellow 
band, but more proximally situated, another band may develop which 
is black and formed by an accumulation of melanin-chromatophores. In 
the males the red and yellow may be developed much more intensely than 
is the case in females. 
The red-yellow band of the distal edge of the anal fin is as it were 
prolonged on to the ventral fins, whose morphological anterior edge is 
likewise coloured red, which red passes into yellow again on the inside. 
At the distal extremity of the ventral fins these colours may develop 
more markedly than more proximally. Now the kepala timah usually does 
. not extend the ventral fins fan-like, but on the contrary holds them so | 
that the distal apex of the fore-edge points towards the tail; hence 
the red band of the anal fin is more or less continued in the red bands 
of the ventral fins. Also the red and yellow of the ventral fins may be much 
more intensely developed in the males than in the females. 
But there is a fundamental difference in the colouring of the dorsal 
and caudal fins of males and females. The proximal half of the small dorsal 
fin in both males and females bears, between the afore-mentioned white 
