APPENDIX. 109 



sixth stages. It is quite probable in the near future that only to 

 avoid excessive crowding will any lobsters be liberated at the fourth 

 stage. 



The successful method of rearing the lobsters through the free- 

 swimming stage was the result of many painstaking experiments. 

 Since the idea was hit upon in 1900, it has taken ten years of con- 

 tinued experiments in order to bring the work up to its present con- 

 dition. It can now be truly said that the scheme, as now operated, 

 is entirely practical and successful. The chief obstacles which had to 

 be overcome in reaching success were the serious cannibalism of the 

 larvae, the necessity of crowding them together in order to rear large 

 numbers, the difficulty of supplying them with sufficient food, the 

 parasitic growths of diatoms and protozoa which infect the early 

 stages, and the determination of an optimum current of water by 

 correct adjustment of the angle of the paddle. 



The main feature of the scheme used in rearing consists in keeping 

 the fry in constant motion. This is accomplished by confining the 

 fry in large wooden boxes or tanks which are suspended in the water, 

 and provided with windows of fine mesh wire netting or perforated 

 metal. A two-bladed paddle, not unlike a restaurant fan, is kept 

 revolving slowly in each box at a rate of 9 revolutions per minute. 

 Through their motion the water is kept fresh and the fry are prevented 

 from settling to the bottom. The current of water is made just strong 

 enough to keep them separated, thus preventing them from feeding 

 upon one another, and yet of sufficient strength to keep their food in 

 circulation near them. The proper adjustment of the paddle is one of 

 the most important elements in successful rearing. 



A three horse-power gasoline engine supplies the power for opera- 

 ting the paddles. This power is transmitted by means of steel shaft- 

 mg, and mitred gears from the houseboat (Plates XIII, XIV), in 

 which the engine is located, to the floats attached to the sides of the 

 houseboat. There are two of these floats which are fastened to the 

 houseboat, one on each side, and are composed of a number of raft 

 units bolted together and floated by barrels. The units are construct- 



