A NEW PRINCIPLE OF AQUICULTURE. 



779 



considerable number were caught with a net and transferred to one of the filter 

 cars, in which they have remained ever since. On September 19 their average 

 measurements were, length &^/i millimeters and breadth lo^ millimeters (Mr. 

 Sullivan) . 



On August 3, 13 scallops, measuring between 45 and 65 millimeters in 

 length, were placed in the second filter car after having a deep notch filed in the 

 shell so that the rate of their growth could be determined accurately. On 

 September 18, 11 of these specimens were taken out of the car and were in 

 excellent condition. The notch and the zone of new growth indicated precisely 

 the size and shape of the shell when the scallop was placed in the box. The 

 increase in length was about 20 per cent. The following table gives the measure- 

 ments of these specimens: 



GENERAL APPLICATION OF THE METHOD IN AQUICULTURE. 



There are two great problems in the general question of fish culture to the 

 solution of which the method herein described contributes: 



First, to the problem of hatching and rearing to an optimum size for libera- 

 tion quantities of fishes of economic value for the direct purpose of stocking the 

 waters. The comparative ease of hatching eggs of most fishes has resulted in 

 the establishment of many prolific hatcheries; on the other hand, the number 

 of establishments capable of rearing young fishes and the number of species so 

 reared in confinement are few. A method of culture, therefore, which is capable 

 not only of hatching but of rearing large numbers of fishes of widely different 

 species marks, we hope, a new step in fish culture. 



The second general problern is the ascertainment of the appearance, habits, 

 requirements, and rate of growth of economically important fishes in their early 

 stages of post-embryonic development. As contrasted with the vast amount 

 of investigation of the embryonic stages of development, which has been 

 facilitated by the abundance of readily available material in the form of eggs of 

 all stages, the data relating to the post-embryonic development are almost 

 entirely lacking. Even the identification of the young of many food fishes 

 abundant in their spawning season is at present impossible. A method by 



