284 DR. ARTHUR WILLKY ON 



are often very rich in individuals of Copepoda, Cladocera, 

 Diatoms, and Dinoflagellates. The dominant constituent of the 

 plankton at all times is the Diatom, CoscinocUsciis, which adheres 

 so tenaciously to the bottom of the watchglasses that it obscures 

 the remaining contents. This Diatom genus, togethei- with 

 Bkldiolphia, is recorded as forming the main part of the Phyto- 

 plankton in the brackish water of the Weser river (Ch. Brockmann, 

 1906 ; see A. Steuer, ' Planktonkunde,' Leipzig and Berlin, 1910, 

 p. 36). 



The character of the water in the tract under survey is defined 

 by the predominance of CoscinocUscus. and the value or interest 

 of the records accordingly depends upon this circvimstance. Of 

 special note in this regard was the occasional appearance of 

 FritiUaria hcn^ecdis Lohmann, an Arctic Appendicularian asso- 

 ciated bionomically with the Copepod, Ccdamis finmarchicus. 

 The FritiUaria was always more or less damaged by the force of 

 its impact with the tow-net. The Calamus was very rare and 

 always immature ; each ramus of the fifth pair of legs was 

 bi-articidate instead of being 3-jointed, as it is typically. 

 H. Lohmann ("Die Appendicvilarien der Plankton-Exped.' 1896, 

 Taf. viii. f. 6, p. 49) has recorded F. borealis also from the 

 Antarctic Ocean, but it is not found in the intervening warm 

 regions. L. W. Williams (" Notes on Mai-ine Copepoda of Rhode 

 Island," Am.er. Nat. vol. xl. No. 477, Boston, 1906, pp. 639-660) 

 says that C. finmarchicus appeared abundantly in tows taken in 

 Naragansett Bay in January, but was found at no^ other time. 

 Professor Ramsay "Wright {op. cit. p. 13) says it was very 

 abundant in the earlier part of the summer at Canso. At 

 St. Andrews I noted its occurrence specifically and singly on 

 July 30th and August 5th ; the length was 3 mm. 



The characteristic and abundant Calanoids at this time were 

 Acartia clausi Giesbrecht, Tortamis discaudatus Thompson & 

 Scott, and Eurytemora herdviani Thompson & Scott. Of these, 

 A. clausi was the most abundant ; and this is noteworthy, inas- 

 much as this species was not found at Woods Hole during July 

 and August 1899, althovigh a related species, A. tonsa Dana, was 

 one of the commonest copepods in tow taken from the wharf of 

 the U.S. Fish Commission at that station (W. M. Wheeler, " The 

 free-swimming Copepods of the Woods Hole Region," Bull. U.S. 

 Fish. Comm. vol. xix. pp. 157-192. Washington, 1901). L. W. 

 Williams {o]7. cit. 1906) iound Acartia io?^sa abundant throughout 

 the summer in Charlestown Pond, Rhode Island, where it was 

 the predominant copepod in the tow ; he also found A . clausi 

 abundant in Naragansett Bay in January and Februaiy. 

 Thompson and Scott have recorded A. clausi from the Gulf of 

 St. Lawrence. It is often colovired with blue spots in pairs 

 below ; and it has a large quivering eye with two lenses. 



Toi'tanus discaudatus is chai'acterised by its dark brown caudal 

 furcn with variable and unequal rami, the right larger ; often 



