OF MASSACHUSETTS. 129 



(d) The Color Chart. — The color of the ovaries of a scallop is an 

 excellent test of theii maturity, as when distended with ripe eggs they 

 generally have a rich orange hue. Before and during the spawning 

 season all grades of color from a flesh pink to a deep orange can be 

 found. While doubtless there is considerable variation in the color 

 at maturity, the general average is sufficiently constant to warrant 

 using it as a basis for recording the spawning season. By the use of 

 Prang's color chart a record of the spawning of scallops in the dif- 

 ferent sections was made. At Monomoy Point, by examining the color 

 of the ovaries without injuring the scallop (the valves being merely 

 held wide apart), the same lots of scallops were followed during the 

 entire summer, and the color changes indicative of the spawning 

 season charted at weekly intervals, according to the standard grades 

 of color in the chart. 



(e) Appearance of Set. — By observations of the appearance of the 

 set in different localities, and having already a knowledge of the age 

 of the scallop at this period, the date of spawning could be correctly 

 estimated. The sets, taken on the spat boxes at Monomoy Point, were 

 carefully recorded for four years, and in other localities when oppor- 

 tunity was given. 



(/) Artificial Spawning. — In order to obtain accurate data as to 

 the spawning of individual scallops the following method was em- 

 ployed: a large glass aquarium containing fresh sea water was placed 

 on the warm sand in the sunlight. Small glass jars, each containing 

 enough sea water to cover a scallop, were placed near the aquarium. 

 The scallops were gently scrubbed with a brush, rinsed in a pail of 

 clean salt water, and placed one in each of the small jars, under which 

 dark paper was placed to facilitate detection of spawn. The usual 

 number under observation at any one time was 16, which proved the 

 most convenient number to watch. In order to prevent injury to the 

 developing eggs by contact with metal the temperature was taken from 

 a separate jar containing the same amount of water. The temperature 

 of the water was taken at the time the scallops were put in and at 

 the discharge of the flrst lot of spawn. At each spawning the contents 

 of the small jar was transferred to a bottle labeled with the number 

 of the scallop, number and time of discharge, and examined micro- 

 scopically to determine whether eggs, spermatozoa or both were lib- 

 erated. The animal and dish were rinsed in the pail, fresh water of the 

 same temperature was taken from the aquarium, and the scallop re- 

 turned to its former position. 



Artificial Fertilization. ■ — Two methods of artificial fertilization have 

 proved most satisfactory in the study of shellfish larva: (1) removal 

 of the sexual products by cutting; (2) forcing the spawning, although 

 the former is not as successful with the scallop as with the oyster, 

 as there are certain drawbacks, such as the crushing of the eggs. 



