1 1 AB ITS AND LIFE-HISTORY OF STICHOPUS JAPONICUS. 



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are in the fourth year from the beginning. And as they seem still in 

 full vigor and produce reproductive elements in the greatest abundance 

 it seems reasonable to suppose that they may go on another year, i.e.. 

 on to the fifth year. In other words, one may reasonably suppose that 

 some individuals of SticJiopus japonicus may live two or three years 

 after they reach the adult condition or five years from the beginning. 



From what has been said above, it follows that when these 

 holothurians are dredged in the autumn, they divide themselves mainly 

 into two lots: (i) the adult, and (2) the second year young. During 

 the spring and early summer months, in addition to the above two lots, 

 a third group forms an important element, viz: — (3) the first year 

 young. 



In a previous publication {loc. cit.) I showed that the calcareous 

 deposits of Stichopus japonicus gradually undergo remarkable changes 

 according to age, and I divided the progress of these changes into five 

 stages. On comparing these alterations with the growth of the indivi- 

 duals I find that those in Stage I are the very youngest, those in Stage 

 II are those caught in December, — February — -April of the first year. 

 At the end of the first year and the beginning of the second year 

 (June- August) Stage III is reached. Stage IV occupies the earlier half 

 of the second year (Dec. — Feb., June). By the end of the second 

 year, Stage V. is reached and with it the adult condition. 



The life history as well as the changes of the calcareous deposits 

 may be graphically shown as in the following diagram : 



Stage I. ..Stage II. ..Stage III. ..Stage IV Stage V 



□ □ -□ □. 



1ST YEAR 2ND YEAR 3RD YEAR 



Apr.— July Apr. — July Apr. — July Apr. — July 



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