i8 



COPEPODA 



with a median and a distal Si and the following segments are fused with 4 setae. The labrnm is 

 scarcely different from the preceding stage. Pes I is in the main structured as in the two preceding 

 stages, but the Si of hasp. II is very delicate, the Ri has a fairly well developed articular membrane 

 between the Ri I and Ri II c^ III. The pes II is practically alike the pes III of the stage III, and 

 the pes III alike pes IV (cf. fig. 3 e). The pes IV is alike the pes V of stage III and the pes III 

 of stage I (textfig. 4 b). 



Y. (St. I). Size: Varying from o-8, 0-9 (07 + 0-2) — i-i mm. Specimens from due d'Orleans 

 were i mm. 



The head is more produced than in the following stage without distinct filaments; behind the 

 head 3 fairly distinct somites are seen in addition to the two somites of the iirosome. The antennulae, 

 which scarcely reach the end of the urosome, consist of 11 segments only; proximally 3 indistinct 

 segments are found, the segments 11 — 18 are probably fused and the segments 19—25 are free. The 



antennae and mandibulae are 

 practically as in f$. The nia- 

 xillulae are alike those of 

 preceding stage but the number 

 of setae seems to be somewhat 

 smaller. The maxillae are in 

 main as shown in textfig. 5 b 

 alike f$. The maxillipeds are 

 even more reduced than in 

 the preceding stage, as easily 

 recognised by studying fig. 

 5 b. The Ri, which is only ^3 as 

 long as the basipodite III, con- 

 sists of the long basal segment 

 with two 2 Si and shorter 

 terminal segment with 4 setae. 

 The lateral outline of the labrum and labium are, as seen by comparing textfig. 5 a with 

 3 a, somewhat different from stage III, the longitudinal series of hairs on the oral surface are in 

 the main arranged as in the preceding stages, but the hairs are very short. The lamina labialis, the 

 longitudinal series of delicate hairs in front of it and the serrula sexdentata are scarcely different from 

 preceding stages. The pes I fig. 5 c has 2 wide basal segments without Si. The undivided Ri has 

 7 setae and the Re has 3 Si and 3 Se. The pes II (fig. 5 d) is less slender but in other respects alike 

 pes IV stage III. The pes III is alike pes V stage III. No secretory pores were observed. 



Occurrence etc. Calanus /inmarchicus Gunn. was, as there was good reason to expect, found all 

 over the area explored by the different expeditions. As I have examined a great number of this 

 species from several hundred of samples, I thought it worth while to examine the proportion of the 

 different stages in each sample. As tlie number of specimens, which were originally picked out from 



Textfigure 5. Cal. finmarchicus G. $. (Stage I). 



a. Lateral view of the labrum X 225; b. maxilla and maxillipes X 225; c. pes I 



(perhaps somewhat flattened by the pressure of the glasscover) X 225; d. pes II 



sin. in anterior view. X 175. 



