23 THE AMERICAN NATURALIST. [VoL. XXXIV. 
small mussels, which, however, the starfish could not or would 
not open, and on August 16, after a period of thirteen days, 
they had not grown at all. From this time they were pro- 
vided with an abundance of their usual food — barnacles — and 
grew with great rapidity, as is indicated in the curves. On 
November 12 they measured, respectively, 36 and 41 mm. 
Incidentally curve 4 shows another interesting point, namely, 
that the loss of an arm does not cause a diminution in the rate 
of growth. On September 5 an arm was accidentally torn off, 
yet the rate of growth of the rest of the body was as rapid as 
Fic. 2 A. Fie. 2 B. 
These figures represent two starfishes of the same age (514 weeks). 
before, and as rapid as that of the other starfish (curve 5). 
The rate of growth in the regenerating member is indicated in 
curve 4 a. | 
The age at which the starfish becomes sexually mature also 
depends upon the rate of growth; in other words, a starfish 
must attain a certain size before it may become sexually mature. 
During May, the month preceding the breeding season, nearly 
all the starfishes measuring over 50 mm. (2 inches) are full of 
ripe sex products, and occasionally ripe specimens are taken 
which measure only 32 mm. Larva have been obtained by 
artificial fertilization from parents measuring 38 mm. Now 
many of the starfishes raised in the car were considerably more 
than 38 mm. in length on October 25, three months after 
