124 



TAGE SKOGSHEFC 



l.itj luiu. 

 4,16 „ 



o,2l) mm. 

 5,20 „ 



t),49 mm. 

 6,60 „ 



8,13 mm. 



10,21 mm. 

 10,16 „ 



The prineipU. 



hat is thf value of 

 this principled 



were examined were measured fmiu the tip of the rostrum to the 

 e. ,,the length of the larvae increases uniformly at 



The specimens that 



tip of the telson. I 



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 

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

 above in order to calcidate 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 from the work mentioned. Thus we read, pp. 96, 97: „In table 24 

 I have recorded the molts of eight lobsters varying from 5^2 to 11^ inches in length. The 

 actual increase in length varied from 1 inch to l^/o 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. 



F. H. Herrick's 



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



