126 



TAGE SKOGSBERG 



'■'. //. Fowler's III- 



I'i'sligations on tlif 



(htrnrods, Homanis 



and Cnrciniis. 



lirou/is's laiv an fur- 



iiiulaled by (!. II. 



Fuivler. 



JJtilocyjinJ'-. 



The agreemeut between the lengths of the first ten larval stages as actually determined 

 by F. H, Herrick and given in Table 25 and the calculated lengths must — when one considers 

 the comparatively small number of specimens measured — be described as striking. 



These facts seem, of course, to a great extent to support the idea that the principle 

 used by W. K. Brooks for the Stoma to pods is of universal application. 



The only writer who has dealt in more detail with this problem is G. H. FowLBR in a 

 work, 1909, on the plankton Ostracods collected during the cruise of H. M. S. Research 

 in 1900. The result of this study is particularly noteworthy, as G. H. FoWLER was of the opinion 

 that he could show that the above-mentioned principle applied throughout the whole Halo- 

 cyprid group. It was also applied to Cypridina (Macrocypridina) castanea G. S. BRADY. 

 Homarus americanus MiLNE EDWARDS and Carcinus maenas Leach. 



On p. 224 of this work G. H. FOVVLER suggests that this principle should be called 

 ., Brooks's L a w", ,,in honour of one of the most ingenious of recent naturalists" and he formu- 

 lates this law in the following general way: ,,D u ring early growth, each stage 

 increases at each moult by a fixed percentage of its length, which 

 is approximately constant for the species and sex." 



The following examples of the applicability of this ,,law" in the Halocyprid group are 

 given in this work: 



Halocypris glohosa (C. Claus). 



Stage 1. 

 Mean 2.51 



Stage 11. 

 Mean 1.5'i 



Stage V. 

 Stage m. Stage IV. ^^^^ 



Mean 0,95 Mean 0,61 q.q 



l-i'Mi^tli in rum.: 

 Xiinibrr of $ nii-asnri 



Total specimens measured: 315 ?. 



,, Considering the scarcity of the smaller specimens, the response of the mean to 

 Brooks's law is good: —0,37 x 1,62 = 0,59; 0,59 x 1,62 = 0,95; 0,95 x 1,62 ^ 1,539; 

 1,54 X 1,62 = 2,49" (p. 278). 



Conchoecia spinifera (0. Claus). 



stage II. 

 Mean 2,12. 



Stage III. 

 Mean 1,44. 



Stage IV. 

 Mean 0,98. 



Stage II. 

 .Mean 1,80. 



Stage 111. Stagc> l\. 

 Mean 1.41. Wt-.m 1,03. 



Total specimens measured: 59 V + 32 cJ- 



„The females, although few, respond well to Brooks's law: — 0,98 x 1,47 = 1,44; 

 1,44 X 1,47 — 2,11. There were only three males at Stage IV., a number which cannot be 



