136 TAGE SKOGSBERG 



The growth factor determined empirically = 1,22. 

 The average lengths calculated theoretically are: 



Stage VII Stage VI Stage V Stage IV Stage III Stage II Stage I Mature 

 20d 24d 29d 35d 43d 52d 63 d 76d 



Actual lengths: 



17— 21d 25— 27d 28— 30d 34— 36d 41— 43d 50— 52d 60— 63d ? 73— 77d? 



■ ■ 57d(J 62(J 



Cyprid'ina ( Vargula) nurvegica. 



All the sjjecimens of this species that are dealt with below, mature males and females 

 and larvae, were collected at Lofoten at the same locality and on the same occasion by Professor 

 G. 0. Sars. There seems to be no doubt that all the specimens investigated really belonged 

 to this species. Only two representatives of the sub-family Cypridininae seem to exist at the 

 west coast of Norway, namely CU/pridina (Vargida) norvegica and C. (V.) megalops. There 

 seems to be no great difficulty in distinguishing these forms even during the larval stages; see 

 for instance, the endopodite of the second antenna. 



Five free-living larval stages could be distinguished. 



General description of the larval stages: — 



In the case of the four youngest of these five larval stages I did not succeed in distinguishing 

 with certainty between males and females by means of dissection. Even in the last larval stage 

 it is almost impossible to distinguish the two sexes except by means of a close investigation 

 of the rudiments of the sexual organs. In the mature stage there is, as will be seen in the special 

 part of this work, a close agreement between males and females; differences are merely to be 

 found in the shape of the shell, the first antenna, the mandible and the furca. These differences 

 are almost entirely absent even in the oldest larval stage. In this stage the shape t)f the shell 

 is almost the same in both sexes, closely resembling that of the mature male, i. e. with a distinctly 

 marked posterior corner; the first antenna is practically alike in both sexes and the 

 mandible as well. In this larval stage, as in Stages II — IV, f u r c a 1 claws nos. 2 

 and 4 are united to the lamella, as on the furca of the mature female; claw no. 3 is, like the 

 others, well marked off basaUy. In Stages I — IV, as in the mature individual, furcal claw no. 3 

 is somewhat shortened and weakened. In the youngest stage observed by me. Stage V, the 

 two distal furcal claws dominate very decidedly over the proximal ones, from which they 

 are also separated by a rather well marked gap. In this stage furcal claw no. 2 is imited basally 

 to the lamella; the other furcal claws are well marked off basally. The number of the furcal 

 claws increases by one for each stage: Stage V has 4, Stage IV has 5, etc. 



Apart fi'om this these larval stages agreed very well with the above-described five 

 oldest larval stages of Cypridina (Doloria) pectinaia. It seems to me quite certain that they 

 correspond to five moults. 



Measurements: — 



From the above-mentioned locality 72 specimens of tliis species were examined. The 

 measurements of the shells gave the following results: , 



