818 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [66] 
which may have settled upon them. The only disadvantage of this sys- 
tem is that the planks or frames, the latter especially, decay quite tap- 
idly by a continuous stay in the water, frequently causing the breeder 
the loss of his harvest or obliging him to entirely renew his apparatus. 
And here one cannot replace the wickets with metal, since the spawn 
of these mollusks will not voluntarily attach themselves to metal. So 
this apparatus will have to be used simply as a collector, and in numer- 
Fic. 22.—Raft collector. 
ous cases it can be of great service to breeders, when, for example, the 
requirements of navigation do not permit the use of fixed apparatus. 
It can also be employed with success in the culture of oysters, when, 
because of the deposit of mud, they cannot be placed upon the bottom 
of the claires. In this case the rafts, covered with young during the 
spawning season, can be floated at the surface and the mobility of the 
frames or slats will allow of the oysters being kept free from mud while 
the condition of light and heat may be varied at will. 
CHAPTER VI. 
REARING OF LOBSTERS AND OTHER CRUSTACEANS. 
In order to accomplish the task which we have undertaken, it now 
remains for us to speak of the processes which can be employed in the 
multiplication of crustaceans, such as crabs, lobsters, and the like. 
While the eftorts at artificial reproduction and multiplication of cray- 
fish in fish-ponds may be successful, and while the fecundated eggs of 
