146 TAGE SKOGSBBRG 



The agreement between the last number and the length of the mature female is of course 

 striking. There were, however, no larvae with shells 0,625 mm. long in this tube. In order, 

 if possible, to be able to complete the chain of development of this species, I went, however, 

 to the sample of sand etc. from which the specimens dealt with above had been picked out. In 

 this I found two complete individuals, clearly larvae in the last larval stage, and one valve 

 which certainly belonged to this species; these individuals had shells from 0,62 — 0,65 mm. in 

 length. The largest specimen was a male; 0,65 x 1,25 = 0,8125, i. e. about the length of the 

 mature male. 



This example seems to show that in the case of species with a relatively constant length 

 of shell we may expect a far-reaching agreement even in those cases where only a small material 

 is present. 

 Grnwih-fnrtor. We must uote the very slight difference in the growth-factor in different species: 



Cyfridina (Doloria) pectinata = 1,22, Cypridina (Vargula) norvegica = 1,21, Philomedes 

 globosa -= 1,23, Krithe sp. — 1,245. 

 Excfption!! to this If thus a number of cases agree particularly well with Brooks's law, there are, on the 



/('/"' 6'" //""flwer other hand, a great many exceptions to this law to be noted. It is certain that the law is 

 by no means absolute. It obviously applies only with a number of restrictions and with certain 

 assumptions. 



This has already been pointed out by G. H. FOVVLER himself. This investigator pointed 

 ont, 1909, p. 258, that it seemed to him possible that not only the average lengths and the 

 growth- factors employed by him but also ,,the law itself, as here phrased" are approximative. 

 As is seen above this author has shown that the same growth-factor does not presumably apply 

 to all stages in large forms with many moults (Homarus, Carcinus). He states on p. 258 that 

 this is presumably true ,,even in Ostracoda of small size and few stages". We find this latter 

 assumption true in the case of the males of Cypridina (Doloria) peciinata and Cypridina 

 (Vargula) norvegica. On the other hand there are no such cases in G. H. Fowler's own examples. 

 Krithe sp. shows obvious variation with regard to the growth-factor. The larvae of 

 Conchoecia elegans can certainly be divided into well distinguished categories of length 

 — contrary to what G. H. FoWLER observed — but they do not permit of any simple application 

 of Brooks's law. Males and females have different growth-factors at the change from Stage II 

 to Stage I and at the change into the mature stage. It is to be noted that the growth- 

 factor is about the same for males and females at the transition from Stage II to Stage I. 

 I have also observed other cases that do not conform to this law, for instance Asterope Gtimaldi, 

 a form that I caught in rather large numbers in the harbour at Monaco. 



We must note that in the cases in which there was agreement with Brooics's law 

 all the specimens that were investigated were caught at the same locality and on the 

 same occasion. On the other hand the water in the harbour at Monaco is subject to great 

 variations and the same is true, though not to such a great extent, of the water in the 

 Bay of Villefranche. 



On pp. 227 and 228 G. H. FoWLER points out (1909) that it will probably appear 

 that the growth-factor is not quite identical for the same species and sex ,,at every 



