800 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [48] 
we have just said in regard to marine plants applies equally well to 
mussels when it is desired to replace them with oysters. Frequent 
dredgings will be necessary in order to remove the greater number of 
these animals, whose presence, moreover, nearly always coincides with a 
muddiness of the bottom, and necessitates, in this case, a cleansing of 
the bottom as indicated above. But the mussel is essentially rustic, 
if I may be allowed the expression, and accommodates itself to nearly 
all conditions of bottom, so that when the mud has been taken away 
and the mussels have all been scraped up, it will be nene the less nec- 
essary to pay frequent visits to the collecting apparatus and carefully 
remove ail the groups of mussels, large or small, which may be discov- 
ered. When the multiplication of the oyster is well assured, and it 
covers all the bottom without leaving any vacant places, this vigilance 
may be relaxed a little, for although the mussel, when it can invade a 
locality, is a redoubtable enemy to the oyster, the reverse is also true, 
and the presence of a bank of oysters in fine growing condition is suffi- 
cient to keep the mussels from such preoccupied grounds. 
Emergent and non-emergent bottoms.—Finally, the marine oyster terri- 
tory can be divided into emergent and non-emergent bottoms. The first 
are found all along the shores of the ocean and the British Channel, and - 
consist of those lands which are left uncovered, either at every tide or 
at the spring-tides, thus exposing for a length of time to the air and 
light, which may amount to several hours per day, the marine animals 
which inhabit them. The second or non-emergent lands lie on the ocean 
coast and join the emergent lands. ‘They are never exposed by the 
withdrawal of the water. Upon the coast of the Mediterranean and 
other inland seas, where the action of the tide is scarcely felt, all the 
lands are non-emergent. Both kinds are suited to the cultivation of 
the oyster, but to a variable extent, dependent upon circumstances. 
The emergent lands, since they are frequently uncovered, have the great 
advantage of facilitating all the labor necessary to their management, 
the sorting, the arranging, and the gathering of the oysters, all being 
done without trouble when the surface is free from water. But the oys- 
ters ought not to be arranged indiscriminately, old and young together, 
for a long sojourn in the air, exposed to the fierce heat of the sun in 
summer and the hard frosts of winter. The young oysters would surely 
perish by a too prolonged exposure where older oysters might exist with- 
out special damage. One should then, if possible, arrange to have in 
connection with his emergent lands a certain amount of territory which 
is never entirely exposed, and upon which the collecting apparatus with 
the young growth can be placed, and the younger oysters also deposited. 
Then as these oysters acquire a suitable size and the power of resisting 
external conditions they can be moved forward, first to that portion of 
the territory which is uncovered only a short time each day, then to 
where the water leaves it for a little longer period, and so on gradually 
advancing, until the oysters shall be arranged in a series according to 
