ANNALES DE L'INSTITUT OCÉANOGRAPHIQUE 5 



of the ani mal communitieshad been made, though I felt convinced from these older dred- 

 gings, that such communities must exist. I had noted the enormous differences in the 

 contents of the dredge at different places, but to express these differences in ivords was 

 impossible at that time ; the long lists of species were too overwhelming, for I did not 

 know, that the one species was of any more importance than the other and further, the 

 dredge could not inform me, which of the species were of greatest importance. 



N° i5. • 

 Kattegat. E. of Hulsig. — Fine sand. — Depht 7 meters. 



July 7, 191 1. 



pr. 1 m* 



Tellina fabula 



Solen sp 



Mactra subtruncata juv. . 



Venus gallina 



Montacuta ferruginosa. .. 



Natica catena 



Bela turricula 



Lacuna divaricata 



Aricia armigcr 



Nephlhys sp 



Ophelia limacina 



Pectinaria koreni 



Ophioglypha tcxturata. . . 

 Echinocardium cordatum 



Gammarida; 



281,088 



9,36) 



Fig. 3. — Animals on the Sea-bottom, pr. 1 m*. Kattegat. 



Before going further, I must try by means of a few examples to show the different pic- 

 tures of animal life on the sea-bottom given by the dredge and the bottom sampler when 

 used at the same place in the sea (see fig4). To obtain as accurate a picture as possible of 

 what the dredge takes of the animal life on the sea-bottom, two buoys were thrown out 

 and anchored at a certain distance from each other and the dredge was towed from the one 

 to the other. From the width of the dredge and the distance betwen the buoys, the area 

 dredged over was estimated to be about 75 m 2 . Thereafter, 5 samples of 0,2 m 2 were 

 taken up with the bottom sampler, thus 1 m 2 altogether; the second experiment contained 

 only o,5 m 2 . The contents of the bottom sampler are indicated in the two first columns 

 of fig. 4, that of the dredge in the two last. In the two central columns the quantity is 

 given of common animals, which are living in the large area worked over by the dredge, 

 as reckoned from the results obtained with the bottom sampler; if the bottom-sampler 

 had been used over the whole area it would certainly also have captured the less frequent 

 animals taken by the dredge, such as larger rapacious Gastropods, Pagurus, large Kchi- 

 nids, etc. 



