Although this is of importance in the basic understanding of the food cycle, it is, in a way, less important in understanding the needs of such forms. The existing doubts are largely concerned with the question of whether the cultures used were bacteria-free. Under natural conditions there are always bacteria present, and we know that nannoplankton grow particularly rapidly when organic matter is present, regardless of whether they assimilate it directly or through the intermediate step of bacteria. The same is true of many non-planktonic protozoa and probably of some higher forms too. A large group of marine animals, ranging from the simplest to the highest forms, consists of filter feeders. These remove particulate matter, detritus, or small animals and plants from the water by means of cilia, mucous nets, setae, etc. Our most extensive knowledge of the food requirements of these comes from the copepods.
Although there is evidence of a certain amount of selection of particular food items, in general they filter the water at a uniform rate regardless of its food content.
scholarships for single mothers
