studies on marine Osfracods 145 



at the transition from Stage II to Stage I and between the latter stage and the mature stage. 



57 d: 51 d = 1,108; 62 d: 57 = 1,109. 



Gypridina (Vargula) norvegica: In this the agreement between the theoretically calculated 



lengths and those actually observed may be said to be surprisingly great. Here too the males 



increase somewhat less rapidly at the change to the mature stage; 3,27: 2,81 = 1,16. 



Philomedes globosa: The agreement between the theoretically calculated lengths and 



those actually observed is striking; only the oldest larval class of length is somewhat longer than 



it ought to be theoretically. 



Krithe sp. : In the case of this species too it can be said that the growth at the different 



moults is very similar. The relations between the mature stage and the oldest larval stage, between 



the latter and the next oldest larval stage, between this and Stage III and between Stage IV and 



Stage V are really very similar, 1,24 — 1,254; average, 1 ,245. Only at the transition from Stage IV 



to Stage III does the growth seem to have been less, the growth-factor being 1,21. 



In passing I may point out here that a smaller number of specimens of the investigated 



material of this species might have given a considerably more striking agreement with BitooivS's 



law. Growth-factor = the average found above, 1,245. 



15,5 



15,5 X 1,245 = 19,29 



19,29 X 1,245 = 24,0 



24,0 X 1,245 = 29,88 



29,88 X 1,245 = 37,2 



37,2 X 1,245 ^ 46,3. 



In other words, if we use this growth-factor, we obtain theoretically average lengths, 



all of which are within the boundaries of the length classes that were established empirically. 



In passing I may point out here that other Ostracod species as well, of which luifortunately An addu onni 



I had at my disposal only a rather slight material, showed a good agreement with BuoOKS's '■^am/)/<?(n /«(-.«/■ „f 



law. I shall only mention a single one of these here, as it gives a rather good illustration of the 



applicability of this law. 



In a tube of s t r a c o d s from the Falkland Islands that I investigated there were, 



besides mature specimens of a Cythereis species* not previously described, a number of larvae 



which, in spite of a number of differences, were, on fairly good grounds, assigned to the above 



species. At the locality in question the mature specimens of this species were characterized 



by great constancy with regard to the length of the shell; mature males = 0,80 — 0,83 (usually 



0,83) mm. Mature females = 0,77 — 0,79 (usually 0,78) mm. A number of the larvae in question 



measured 0,49—0,51 (average 0,50) mm., others 0,40 mm. For anatomical reasons I concluded 



that they represented Stage II and Stage III. The growth-factor was consequently 1,25. 



0.40 



0,40 X 1,25 =- 0,50 



0,50 X 1,25 = 0,625 



0,625 X 1,25 = 0,781. 



* To be described in a later part of tliis worlc. 

 Zoolog. bidrag, Uppsala. Suppl.-Bd. I. '^ 



