Sliulitis oil inariiii' Ostriicods 143 



Average lengths, expressed in divisions of the micrometer: males, mature ^ 60 d, Stage I = 

 47d, Stage II = 30,7d. Females, mature ^ 57d, Stage I -_ 40,2d, Stage II = 27 d. 

 Gr r w t h - f a c t o r: Males: — 60 : 47 -= 1,277; 47 : 30,7 -^ 1,53 



Females: — 57 : 40.2 = 1,41; 40,2 : 27 1,5. 



Sub-order: CiifriformeM. f'yi"-ih 



In this group eight post-embryonal larval stages have been observed, according to the 

 investigations of C. Claus and G. W. MUller. The number of moults seems to be constant 

 within the whole group. The development is very similar in the different families; cf. G. W. 

 MilLLER, 1894, pp. 175—183. 



The species of this group investigated by me have a post- embryonal development that 

 corresponds exactly to that which has been established by C. ClaL'S and G. \V. MClleij for other 

 forms in this group. Because of this I have omitted to give descriptions of the observed classes 

 of length below. 



Krithe sf* 



All the specimens of this species dealt with below^ were collected at the same locality on 

 the same occasion: the Bay of Villefranche (Maritime Alps, France), at a depth of 95 m. on 

 January 19th, 1916. A considerable number consisted of empty shells. This fact does not, 

 however, make their determination less certain, as this species differs greatly from all other 

 species from the locality mentioned by the shape of its shell. The Ostracod fauna from this 

 locality was not at all rich in species, and I had obtained a thorough knowledge of it by means 

 of a large number of dredgings. 

 Measurements: — 



428 specimens of this species from the locality mentioned were examined and measured. 

 The measurements of the lengths of the shells gave the following result, which is presented 

 graphically in fig. XXIII. 



As this table shows, the specimens that were investigated may be divided into six distinct 

 classes according to the length of their shells. Of these class 43 — 48 represents mature individuals. 

 The males and the females were of about equal lengths. 



It is practically quite certain that each of the five larval classes of length really represents 

 a moult. A decided argument in favour of this is the fact that I succeeded in observing in an aqua- 

 rium how individuals of one class attained the length of the next largest length class by one moult. 

 Two females in Stage I, with shells 36 and 36,5 divisions long respectively, attained a lengtli 

 of about 44 divisions after one moult. One larva of Stage II, with a shell about 28.5 divisions 

 long, had after one moult a length of about 35 divisions. On all the occasions the moult occurred 

 from two to five days after the beginning of the aquarium life. 



Average lengths for the six classes of length mentioned above: 

 Mature = 45,1 d; Stage I - 36,12 d; Stage II = 28,8 d; Stage III =- 23,23 d: Stage I \' 

 19,2 d; Stage V =- 15,5 d. 



• This sppcics will hf drm iilM'<l in mniN- di'lail in m fi)llii\viiii,' |imiI <>f this wnik. 



