216 THE ROYAL SOCIETY OF CANADA 



The position of the one seta was opposite the middle of the distance 

 between the two distal internal setae, while the two Se were each oppo- 

 site an internal seta. This suggests that two Se had been replaced by 

 one Se, and we would expect to find the one Se double the normal 

 size, but this was not the case. 



B. Calaniis hyperhoreus 



This species was not very abundant in the tows, only twenty 

 individuals being obtained from a vertical haul taken at "Prince" 

 Sta. 3, May 24th, 1916. There is a regular row of large coxal teeth on . 

 p5 in Stages V and VI, but unlike C. finmarchicus, there are no coxal 

 teeth in stage IV. The teeth are larger and fewer in number than in 

 C. finmarchicus and the row does not reach the distal end of the joint. 

 Like C. finmarchicus there may be two Se on each Ri of p5, or only one. 

 Of three females examined, two of them had one Se on each Ri; the 

 other had one Se on the right and two on the left. The occurrence of 

 similar variations in the two species is a point of interest. 



Final Exuviation of Eurytemora and Tortanus 



Eurytemora herdmani, Thompson and Scott, was the most abund- 

 ant copepod in the tows taken from the wharf of the Biological Station 

 during the latter part of June and first part of July. Unlike Calanus 

 which has no exuviation after it has reached the female 9 1 stage, 

 Eurytem-ora exuviates from an immature stage of the female (Fig. 36) 

 to the mature female 9 2 (Fig. 37). In 9 1 the postero-lateral angles 

 of the forebody are produced as soft points, each with a single sub- 

 apical spinule, and are not expanded into the characteristic winglike 

 structures of 9 2 (Fig. 37). It is further distinguished from 9 2 by 

 the structure of the fifth swimming feet (Figs. 38, 39). In 9 1 the 

 undivided rami of p5 have each a smooth claw-process directed 

 obliquely inwards and distal, not bent so as to lie parallel with the 

 distal part of the ramus which is not articulated in this stage; there 

 is no external seta on the second basal joint, nor is there a cilium 

 proximal to the first external seta of the ramus as in the adult. 



One measuring 1 • 2 mm. in length was kept alive three days in 

 filtered sea water in a Syracuse watchglass covered by another. On 

 the third day (June 14th), although still alive, it had ceased darting 

 about and on close examination was discovered to be in a process of 

 ecdysis to 9 2. Its appendages were moving and heart beating 

 intermittently. At 9 a.m. on June 15th, the heart had stopped beat- 

 ing, but there was still an occasional quiver of the appendages and a 

 slight peristaltic movement of the intestines; the exuvia had partly 



