4O CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 



RATE OF GROWTH 



The rapidity with which starfishes increase in size, and the age 

 at which sexual maturity is attained, have long been subjects for 

 discussion among zoologists. A number of years ago Alexander 

 Agassiz estimated the growth and age of the common starfish, 

 and came to the conclusion that it required about fourteen years 

 for the animal to reach its full development. It was thought 

 to begin to spawn before that time, apparently at six or seven 

 years of age. 



Professor Mead, however, has settled this point beyond dis- 

 pute* by actually rearing large numbers of young starfishes from 

 the time when the free-swimming larvae attach themselves to 

 the eelgrass and other objects in preparation for their trans- 

 formation to the adult form. 



By keeping these young starfishes in aquaria and submerged 

 cars and feeding them regularly, a most surprising rapidity 

 of growth was found to result. On June 2Qth the stars measured 

 on the average only about imm. from mouth to tip of arm; 

 on July 1 8th, 5mm. ; July 26th, 9mm. ; August i8th, i8mm. ; 

 Sept 26th, 35mm.; and on Oct. 25th, 54mm. Such stages of 

 growth are represented in their natural size on Plate VI, from 

 Mead's report in the Bulletin of the U. S. Fish Commission 

 for 1899. 



Figs, i to 3, on Plate VI, show small individuals taken from 

 seaweed soon after having completed the free-swimming stage. 

 Fig. 4 shows the average size found on eelgrass and seaweed 

 about two weeks later, July 15, and Fig. 5 a large individual 

 of the same age which was reared in a submerged car and well 

 supplied with food. A similar individual reared in car, three 

 days later, is shown in Fig. 6 ; and one after eight days more, July 

 26, in Fig. 7. Figs. 8, 9, and 10 indicate the size of the young 

 starfishes about four weeks, six weeks, and nine weeks after 

 having completed the free-swimming stage. Fig. n shows the 

 growth in three weeks more, while Fig. 12 indicates the size 

 attained by a large individual reared in submerged car with 

 an abundance of food, at about 4 months of age. 



* Mead, A. D., On the Correlation between Growth and Food Supply in Starfish. 

 American Naturalist, vol. xxxiv, 1900. 



