204 College of Forestry 



into herbivores, detritus eaters, and carnivores. The Danish 

 investigators, headed by Dr. Petersen ('ii, '13, etc.) have 

 laid great stress upon the value of the bottom material, called 

 by Petersen " dust-fine-detritus " (see Baker, 'i(3, pp. 1 14-120; 

 also Petersen, '11, p. 6) as food for many animals, especially 

 the invertebrates. Blegvad sums up his investigations in the 

 following words : " Detritus forms the principal food of 

 nearly all the invertebrate animals of the sea bottom, next in 

 order of importance being plant food from fresh benthos 

 plants. The value of live phytoplankton in this connection is 

 absolutely minimal, amounting in any case to nothing more 

 than an indirect significance through the medium of the 

 plankton cocepods." 



Blegvad also sums up his results in a very interesting table 

 (p. 74) in which the various bottom inhabiting animals are 

 listed according to their food habits. Although the fresh- 

 water animals of Oneida Lake are not subject to exactly the 

 same conditions as the marine animals of the Danish waters, 

 they are nevertheless subject to the same method of treatment, 

 and in Table No. 52 they are listed following the method of 

 Blegvad. It is to be noted that this table is provisional, many 

 of the groups not having been sufficiently studied as to their 

 food habits. The table may serve to form the basis for future 

 work.* 



* The terms used in the table have the following meaning: 



Detritus caters. Living on the animal and vegetable matter held in 

 suspension in the water or deposited on the bottom, including some 

 plankton and some carrion. 



HrrbivDroiis-dctritus eaters. Living on both plants and detritus. Eat 

 carrion also. 



Hcrhivorons and carnivorous. Living on both fresh animals and 

 fresh plants. 



Carnivorous-detritus eaters. Eating carrion as well as fresh animal 

 food. 



Carnivorous eaters. Living only on fresh animal food. 



Herbivorous eaters. Living only on fresh plants. 



By detritus is understood " such dead or dying (decomposing) 

 organisms or portions of same, whether of vegetable or animal origin, 

 as are found in suspension (or solution) in the sea water or deposited 

 on the bottom." It is believed that the fine dust-like covering of the 

 bottom deposits in our lakes, together with the fragments of plants and 

 animals, is homologous with the detritus thus characterized by Blegvad. 



