16 



MARINE AND FISHERIES 



6-7 EDWARD VII., A. 1907 



The excellent account by Lokmann of the forms belonging to this class, secured 

 on the Plankton Expedition, renders diagnosis easy of the three forms found at Canso. 

 Two families are recognized by him, one Kowaleskidse, distinguished by the absence 

 of the endostyle, the other Appendicularidse, embracing all the remaining genera 

 of the group. It is to the latter family that all the three species under consideration 

 belong. The first of these to appear during the early part of July was Fritillaria 

 horealis Lohmann (Plate VII., fig. 11). The length of the trunk of the example 

 figured was 540/^-, of the tail 1 mm. Projecting from the lateral edges of the trunk 

 posteriorly are two processes like those which mark the species F. pellucida. No 

 signs of the ^ house ' of the species were observed. 



The two remaining species belong to the genus Oikopleura, distinguished from the 

 foregoing by the plumper form, and by the circumstance that the fin of the tail begins 

 at its attachment, not at some distance therefrom as in Fritillaria. 0, 

 lahradoriensis Lohmann replaced the foregoing during the latter end of July, 

 while 0. dioica Pol was very abundant in the latter part of August. These can 

 be at once separated by the fact that the former has some 16-18 globular ' sub- 

 chordal ' cells under the notochord in the latter half of the tail, while 0. dioica (figs. 

 12, 13) has two stellate cells in the same position. It is the only dioecious species; 

 ripe females with eggs 70, u in diameter were observed on August 20. Although like 

 other strictly pelagic creatures for the most part transparent, 0, dioica shows some 

 traces of pigment in its intestinal tract, the oeosphagus having a faint pinkish hue, 

 while the rest of the intestinal wall, and especially the large gastric cells of the left 

 compartment of the stomach, are decidedly violet. This species appears to live on 

 • a small green Flagellate (8, a in diameter) which I only observed in its stomach. 



Note. — Through inadvertence some of the literature has been cited in the text, 

 and some by the numbers which follow: — 



No. 1. Hensen. — Ueber die Bestimmung des Planktons. — Berlin, 1887. 



No. 2. Schiitt. — Die Peridineen der Plankton-Expedition. — Kiel and Leipzig. 

 1895. 



No. 3. Jorgenson.^ — Protophyten and Protozoen. — Bergens Museums Aarbog, 1899. 

 No. 4. Gran. — Protophyta. Norwegian North Atlantic Expedition. 

 No. 5. Lemmermann. — Nordisches Plankton. — 2te Lieferung. 



No. 6. Jorgenson. — Tintinodeen der Norwegischen West-Kiiste. Bergens Museums 

 Aarbog, 1899. 



EXPLANATION OF PLATES. 



PLATE I. 



Fig. 1. Exuviaella marina, x 600. 



2. Prorocentrum micans. x 600. 



3. Pyrocystis lunula, globular stage, x 250. 



4. " with contained crescents. 



5. Pyrocystis lunula with contained Gymnodinia. x 250. 

 5a. A single Gymnodinium. x 500. 



6. Pyrocystis sp. x 150. 



7. Gymnodinium sp. x 400. 



8. Pouchetia ochrea. x 400. 



9. Gymnodinium gracile. x 250. 



10. Dinophysis norvegica. x 450. 



11. Dinophysis rotundata. x 450. 



