PLATE LVII. 
species, either from the condition of the fish, its age, or the par- 
ticular season of the year. Sometimes they are remarkably vivid, 
at others scarcely discernible, and even in the same fish they appear 
much stronger, after scales on the sides are partly rubbed off. The 
lateral spots by which the shad is distinguished, in some individuals 
amount to ten: they do occasionally occur with only four or five, 
but the intermediate numbers about seven or eight are the most fre- 
quent. An opinion prevails, that as the fish grows old, those spots 
fade away, and at last entirely disappear. Independant of those 
lateral spots, there are commonly two others upon the tail, one of 
which is situated on the upper, and the other on the lower edge, 
contiguous to the base. \ 
The Shad is known as an inhabitant of many parts of the world. 
In the Mediterranean, the Persian, Egyptian, and American seas, 
we learn it to be most abundant : it also swarms in those of the 
northern parts of Europe at some times of the year. The haunts 
of this fish are the open sea, which it leaves at certain seasons, in 
order to ascend rivers to deposit its spawn, in places of convenient 
security. 
The time of its appearance in the same rivers is pretty constant, 
but they do not ascend all rivers at the same time. This may vary 
according to the nature of the climate, and may be also governed in 
some measure by the temperature of the season. In the Nile for 
instance, it is seen in January, or even in December. It passes 
from the sea up the Rhone in March : in the Wolga, Rhine, and 
Elbe, it is seldom observed till April or May, and in some of the 
rivers on the continent its appearance is so regular about the month 
of May, and not before, that it has acquired the name of May. 
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