202 SMITHSONIAN MISCELLANEOUS COLLECTIONS [voL. 48 
’ 
posititious “new genera” have been based almost entirely on 
pharyngeal bones and teeth. 
SEXUAL DIFFERENTIATION 
As the breeding season approaches, and during that season, the 
males of many species assume and exhibit brilliant colors and 
marked cutaneous excrescences. ‘The colors are in some extremely 
vivid and chiefly bright red, blue, and steel color; the excrescences 
or tubercles vary in position; they are mostly on the head and espe- 
cially about the snout, but in some are also developed on the sides 
and on the fins. These excrescences are correlated with the manner 
in which the males approach the females and attach themselves 
during the period of oviposition, and there appears to be consider- 
able variation, according to species, in the manner of juxtaposition 
of the male and female during the process of oviposition.* 
The eggs are mostly laid on the ground and, after fertilization by 
the males, left to themselves. Of some species, however, the par- 
ents, generally only the males, assume charge of the eggs and 
watch over them until they are hatched. None of the European 
fishes are known to do so, but the American horned dace (Semotilus 
atromaculatus), black-headed dace (Pimephales promelas), and 
stoneroller (Campostoma anomalum) do, and their actions have 
been especially studied by Professor Reighard. But the most 
remarkable mode of oviposition is that manifested by the Central 
European bitterling (Rhodeus amarus). The sexual differences 
are well marked; the male being larger and brilliantly colored in the 
breeding season. The ripe female has a long ovipositor in front 
of the anal fin, by which she introduces egg after egg into a gill 
of a fresh-water mussel (Unionid) and therein the egg is developed 
and hatched. Nothing like this has been found in America where 
the mussels so abound, but it is not impossible that analogous species 
may occur here. 
Naturally the habits of the common and widely distributed carp 
are best known, and a summary of what has been learned about it 
may give not only its history but hints as to poe to be observed 
for other species of the family. 
LirE History OF THE CARP 
The genus Cyprinus, though designated as the type of the family 
and giving name to it, is only to that extent typical, it being a group 
1 Another kind of sexual differentiation will be noticed in connection with 
the Tench (p. 210). 
