182 University of California Publications in Zoology [Vol. 16 



organisms are used as food and in what numbers. If we can discover 

 liow much food is taken by Calanus, even as a very rough average 

 from a large series of observations, we shall have to be satisfied that 

 the food requirements are met, whether the actual results conform to 

 the theoretical needs or not. 



SUMMARY 



1. Particles that float (such as grains of carmine) are carried 

 toward the mouth by water currents set up by movements of the head 

 appendages. The particles are definitely directed by means of the 

 sides of a sort of trough formed by the long bristles of the anterior 

 maxilliped. These appendages are stationary most of the time. 



2. There is formed a little pellet, which is held immediately be- 

 hind the mouth and then taken in when the esophagus is dilated. 



3. It appears that the oi'dinary movements of locomotion are not 

 necessarily those that cause the formation of the pellets, since animals 

 may be kept for hours in water to which carmine has been added 

 without ingesting the particles, while in other cases the color appears 

 in the intestinal tract in a few seconds. 



4. An examination of the digestive tracts of several species of 

 marine copepods shows that diatoms are the organisms whose remains 

 appear most often, but in many cases the tracts are empty or contain 

 only bits of debris and more or less of a green mass. 



5. The amount of food that is indicated by the intestinal contents 

 is surprisingly small in the majority of cases, and especially so when 

 the figures given by Piitter as to the needs of a copepod are considered. 



6. It is likely, however, that the food of these animals consists to 

 an important degree of organisms of the centrifuge plankton which 

 are without shells and do not leave recognisable remains. At any rate, 

 this possibility needs careful investigation before Piitter 's theory of 

 nutrition through dissolved organic material is accepted. 



Transmitted December 27, 1915. 



