fcuRRiE] PLANKTON COPEPODS 217 



separated from the new cuticle. The copepod was transferred to a 

 slide and a coversHp supported by a strip of paper was put over it. 

 This sh"ght pressure caused the exuvia to break away from parts of the 

 body. The new postero-lateral angles of the forebody were freed 

 and showed that they were more expanded and winglike than those 

 of the exuvia. (Fig. 40). The caudal rami, which are 43^2 times as 

 long as they are wide, had partly withdrawn. The p5 of 9 2 could be 

 clearly distinguished within the old cuticle, especially the spines 

 of the claw process of the proximal joint of the ramus and the articu- 

 lation of the terminal joint (Fig. 41). 



In an oblique haul taken from the wharf on June 12, there were 

 many mature females with their ovisacs attached, darting about 

 in the water. One specimen had not less than fifty eggs in its ovisac, 

 each -082 mm. in diameter, and on examination it was found that 

 there were many more eggs in the oviduct. It was estimated that 

 there were enough eggs within the copepod to fill three successive 

 ovisacs. In another specimen the eggs within the ovisac were much 

 farther advanced and were nearly ready for hatching. In fact the 

 ovisac had broken and a few of the nauplii had already escaped. In 

 the same haul were a few males easily distinguished by the naked eye 

 from the females and the other copepods by the scarlet tumefied 

 portion of the right antenna. The right ramus of p5 had a roughened 

 ridge at the end of the terminal joint, but no plumose seta (Fig. 42). 



Tortanus discaiidatus, Thompson and Scott, was usually found 

 in the tows taken from the wharf at the Biological Station in June and 

 July. Although it was not nearly as abundant as Enrytemora yet it 

 could be picked out from the other copepods by its slightly bluish 

 tinge. This colour was due to small dark blue spots at the base of 

 the appendages. Towards the end of June and during July females 

 were obtained with spermatophores attached. 



As in Enrytemora there is an exuviation within the female stage. 

 Tortanus 9 1 is 1-52 mm. in length. There are three segments in 

 the urosome and the rami of the caudal furca are nearly alike (Fig. 

 43). The p5 are 3-jointed, with a plumose seta on the distal basal 

 joint and four delicate spines on the ramus (Fig. 44). Tortanus 9 2 

 is about 2-25 mm. in length, with unequal caudal rami and a clump 

 of stiff cilia on the right side of the second segment of the urosome. The 

 large right caudal ramus has an area of pubescence on the outer surface, 

 and a row of cilia on the inner surface; and the basal portion of the 

 outer seta is enlarged to form a conspicuous process (Figs. 45 and 46). 

 The p5 differs from that of 9 1 by having the ramus smooth and with- 

 out any spines (Fig. 47). Eggs were seen in the ovaries of 9 1 as 



