1916] Esterltj: Feeding ITahits of Pelagic Copepods 175 



It seems clear that the free-swimming copepods must obtain their 

 food in the general way set down above, but some individuals will not 

 ingest particles of carmine under the conditions that others do. All 

 the animals in a watch-glass are in constant activity with the char- 

 acteristic jerky movements, but not all of them will show the carmine 

 in the digestive tract. This suggests that the movements of the ap- 

 pendages that lead to locomotion are not necessarily the ones that 

 cause solid particles to gather in the mouth region. There may be 

 special movements of certain appendages or of parts of them that 

 cause the pellets to form. There is a possibility, however, that the 

 pellets are constantly formed and as regularly rejected by the animals 

 that do not take in the carmine. 



The formation and ingestion of the pai-ticles takes place rapidly. 

 If specimens of Calanus are taken from clean water and put into a 

 watch-glass at the edge of the stage of the microscope and carmine is 

 added, the coloring matter will have been ingested within the few 

 seconds that elapse before the animals can be brought under the 

 objective, and the particles can then be seen as they move back and 

 forth in the digestive tract. On the other hand, specimens have been 

 kept in good condition for tliree or four hours in water containing 

 carmine, and in that time most of the animals did not show the color 

 in the tube. Attention may be called to the similarity between the 

 process of food-getting just described for. the Copepoda, and that in 

 Paramecium, where the oral groove and cilia take the place of the 

 bristles and complex appendages. 



While I have observed the actual ingestion of solid particles only 

 in Calanus, I have often seen the pellets formed by Eucalanus, but 

 they were not taken into the mouth. The figures shown are of Euca- 

 lanus, but the structures are so similar in Calanus that the one will 

 do for the other. The essential occurrences are the same in both these 

 forms, so far as I have been able to determine, though there are certain 

 structural differences in the appendages. 



The question of how marine animals are nourished has caused a 

 good deal of discussion within the last few years. This seems to have 

 been brought about largely by the introduction of Piitter 's ideas. This 

 investigator (Piitter, 1907 a, h, 1909), as is well known, believes there 

 is evidence that the food requirements of many forms can not be met 

 if the animals are dependent on organic material actually ingested. 

 If this is true, there is some other source of utilisable food, and it is 

 found, according to Piitter, in the organic compounds in solution in 



