124 



TAGS SKOOSBBRG 



The principle. 



What is the value o/ 

 this principle? 



F. H. Merrick's 

 uwestigatiotis on thi 

 American Lobster. 



4,16 mm. 

 4,16 „ 



5,29 mm. 

 5,20 „ 



6.49 mm. 



6.50 „ 



8,13 mm. 



10,21 mm. 

 10,16 



The specimens that were examined were measured from the tip of the rostrum to the 

 tip of the telson. I. e. ,,the length of the larvae increases uniformly at 

 each moult by one-fourth of its length before the moult" (p. 105). 



Have we here a principle that can be applied universally? 

 Do the larvae increase by a constant percentage of their length in other Crustacean 

 groups as well? 



W. K. Brooks gives no answer to these questions. And almost all other investigators 

 have, curiously enough, left this question almost entirely untouched, although it seems to merit 

 the greatest possible attention. If we are concerned here with a universal principle, a law, we 

 shall have discovered a method of investigation that would to a very great extent increase the 

 possibility of determining with certainty the species and relative age of the larvae of the Crustacea. 



F. H. Herrick in his important work „The American Lobste r", 1896, has 

 — apparently quite independently of W. K. BROOKS — made use of the principle described 

 above in order to calculate approximately the number of moults of the shell that a lobster of 

 a given, arbitrary length has undergone. 



As F. H, Herrick's exposition of this point seems particularly interesting I shall give 

 a verbal quotation of it fi'om the work mentioned. Thus we read, pp. 96, 97: „In table 24 

 I have recorded the molts of eight lobsters varying from 5 ^ to 11^ inches in length. The 

 actual increase in length varied from 1 inch to 1 y^ inches, and the increase percentage (that 

 is, the ratio which the increase bears to the total length before molting) from 6,66 to 18,18. 

 The average percentage of increase in all these cases is 12,01. 



Table 24. — Increase in the length of lobsters at the time of molting. 



