The ecology and life history The ecology and life history of the common frog (Rana temporaria temporaria) ecologylifehisto00sava Year: 1962 52 ECOLOGY AND LIFE HISTORY OF THE COMMON FROG aguae, specialization has gone so far that each cord has it own tunnel in a divided oesophagus, as shown in Fig. 19. This neat arrangement obviously prevents the ingestion of particles of any great size, and H. aguae is presumably exclusively a microphagous feeder. R. temporaria is more versatile, for it has another method at its disposal. If Fig. 17 or 18 is studied, it can be seen that the direction of the
The ecology and life history The ecology and life history of the common frog (Rana temporaria temporaria) ecologylifehisto00sava Year: 1962 52 ECOLOGY AND LIFE HISTORY OF THE COMMON FROG aguae, specialization has gone so far that each cord has it own tunnel in a divided oesophagus, as shown in Fig. 19. This neat arrangement obviously prevents the ingestion of particles of any great size, and H. aguae is presumably exclusively a microphagous feeder. R. temporaria is more versatile, for it has another method at its disposal. If Fig. 17 or 18 is studied, it can be seen that the direction of the stream of water changes suddenly at the posterior end of the pharynx. This would NOTOCHORD FOOD SEPTUM MM Fig. 19. Transverse Section of the CEsophagus of a Tadpole of Hypopachus aguae Showing the Two Separate Channels for the Mucous Cords throw any large particles into the wide oesophageal funnel by centri- fugal force, and these would be conveyed down the oesophagus by cihary action. It has been suggested that the gill filters are food-collecting organs, and so they are in a hmited sense. It seems to have been overlooked that filters of any kind are always intermittently-operated structures, and that, since they are not ciliated, there is nothing to move food collecting on them to the oesophagus except the water currents, into which the food is probably thrown at intervals by a process of back-
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