A NEW PRINCIPLE OF AQUICULTURE. 767 



foresee that there are any strictly aquatic animals the requirements of whose 

 young may not be fulfilled by means of this method. 



We have developed and applied the method mainly in connection with the 

 hatching and rearing of larval lobsters, but we may assert, without fear of 

 contradiction by anyone familiar with the rearing of lobster fry, that we have 

 done this not because of the comparative ease of rearing lobsters. In the case 

 of all species of fishes which we have attempted to rear the problem is easier 

 than in the case of lobsters. 



APPARATUS. 



GENERAL DESCRIPTION. 



The apparatus as at present installed has proved capable of rearing the 

 larval and young stages of fishes and of invertebrates belonging to several 

 different groups. The main features are as follows : A houseboat consisting of 

 two decked pontoons 4 by 4 feet square in section and 50 feet long held 8 feet 

 apart, the intervening space decked and covered by two houses 10 by 10 feet 

 square and 10 by 20 feet, respectively, flanked on either side by two floats 

 attached to the houseboat and made of 6 by 6 inch spruce timbers bolted 

 together and buoyed up by barrels. The spaces between the timbers of the 

 floats are divided into areas 12 by 12 feet, to contain the hatching cars, and 

 into alleyways about 2 feet wide, to contain the supporting barrels. (See 

 diagram, p. 766, and fig. i, 2, 3, pi. xc, xci.) 



The inclosures for confining the fry are in the form of lo-foot square boxes 

 (fig. 5, pi. xcii) having two windows in the bottom and two windows in two 

 sides, the windows screened, in the case of lobster fry and very small fishes, 

 with fine-meshed woven bronze wire. 



In each box or car a pair of propeller blades, adjustable to various angles, 

 are horizontally placed, attached to a vertical shaft with proper bearings (fig. 

 4, pi. xci; fig. 6, pi. xcii; fig. 18, pi. xcviii). By the revolution of the pro- 

 peller blades the water is kept in circular and upward motion (fig. 4) . The 

 propeller shaft carries at its top a gear which engages a similar one with half 

 the number of teeth borne on a horizontal longitudinal driving shaft. The pad- 

 dle shaft can, however, be instantly thrown out of gear by a lever (fig. 22, pi. c). 

 The longitudinal shaft transmits the power to all the propellers in one float 

 (fig. 2, 3, and diagram). It receives its power from a shaft running trans- 

 versely across the float, the two shafts being connected by mitered gears (fig. 4). 

 The transverse shaft of the float is connected to a similar one across the 

 houseboat by a set of universal ball joints and an extensible shaft and sleeve 

 device, invented for this particular purpose, which allows for several inches of 

 variation in the length of the shafting system (fig. 17, pi. xcviii). The trans- 

 verse shaft on the houseboat runs through the side of the house and inside the 



