poor in zooplankton. The following associated carries the elements of food from the lip cartilage 

 characteristics appeared in the larvae of Anura: into the depths of the cavity. During the depres- 

 an apparatus of lip cartilage which serves for sion of the oro-pharyngeal cavity the gill arches 

 the capture and chewing of the growing plants close due to the contraction of Mm. constr ictoros 

 that serve as basic food, a long convoluted in- branchiales r i.e., the oro-pharyngeal cavity is 

 testine which is suitable for the digestion of isolated from the external gill chamber. The 

 this food, and an external gill concavity which latter chamber is isolated from the outside 

 facilitates the acquisition of a streamlined by a dropping of the walls of its efferent canal 

 body form. The origin of the last item caused and this wall plays the role of a valve. The re- 

 loss of the external gills and the development turn movement of the ceratohyal ia with the medial 

 of hidden homologous gills situated on the cera - ' ends upward takes place during the action of M. 

 tobranctiiaj. j a as in fishes. We were not able interhvo ideus anterior . This muscle contracts* 

 to observe the motion which specially serves for and at the same time lowers the lateral ends of 

 breathing. For this reason the mechanism for the hyoid. Together with the medial ends of the 

 the transport of food, even though there are ceratohyal ia, the fiars reuniens and both copulae 

 peculiar. ties imposed by the development of are raised. However, the M. i nterhvo ideus 

 concealed gills anterior draws the ends of the hyoid not only 



„ . . ± . ventrally but caudally as well attempting to join 



Such an interpretation of the function of them horizontally, 

 the hyobranchial apparatus in the tadpoles is 



confirmed by the absence of gills in the larvae Copula I is hindered by this movement and it 



of Xenopus laevis and by the observation that supports the medial ends of the ceratohvals 



the motion of the hyobranchial apparatus serves Simultaneously with the contraction of the M 



only for the transport of food. interhyo ideus anterior , the Mm. subarcual ,, 'r.r* i 



TL , . and obli q'-l i contract and turn the qill chambers 



The large ood masses entering the mouth in with a movement which is counter to' the movement 



;;;::; e f C ;: d "°" re ""!7 a Chan f in h * m °t'° n °f depression. The simultaneous contraction of 



pattern of the hyobranchial apparatus. In tad- the annuo mont ;„„.,( „ 1 ,. . 



poles, as distinct from the larvae of Urodela, portion of th!f!or of h" "'"it ^ "'1"" 



1- L r r .,. . pun ion ot tne Tloor of the oro-pharvnaeal cavitu 



ingestion occurs by means of frequent oscillations With this a stream of water carrying^" mater a 



which are no of great amp itude. These oscil- changes its direction and enters ^ ™°° Xl\* 



1 . .on, create a weak constant stream of water wh il e the particles of food are rid 



which facili ates the transport of food into the the presence of a special filter apparatus 

 interior of the oro-pharyngeal cavity. Food is 



not captured at a distance. In none of the in- | n the larvae of Phaneroglossa the filtered 

 vestigated forms do the oscillations of the hyo- water exits through the gill slits into the ex- 

 branch. al apparatus occur in the sagittal plane ternal gill chamber, sweeping over the qill 

 as in the larvae of Urodela, but rather in the branches in the process. During the next intake 

 transverse plane. pulse the retained food material is drawn into the 

 T . . , ,. ,. esophagus, while the next lifting of the buccal 

 The depression of the floor of the oro- floor causes the water to be filtered aqain 

 pharyngeal cavity takes place during the motion After entering the external gill chamber the last 

 of the ceratohyal ia and the gill chambers batch of water is expelled. Thus each successive 



H T?^ ^ u V^ *'?? ed9eS d ° Wn " dr ° P ° f the fl00r of the oro-pharyngeal cavity will 



ward. The M. orb i tohyo , deus and M. suspensor i o - cause the water that enters into the esophagus to 



h V°'deus draw the lateral ends of the hyoid up- be further enriched by the food particles which 



ward. Ceratohyal ia turn in the geoquadrate ar- remained in the oro-pharyngeal cavity during the 



ticulation which serves as the only connection of previous elevation of its floor, 

 the hyobranchial apparatus of tadpoles with the 



skull. During this turning, the medial ends of The mechanism of action of the tadpole hyo- 



the ceratohyals, which are spread and thickened, branchial apparatus is characteristic for all the 



are depressed; together with the copula I pars investigated forms. It is remarkable that one 



re>jniens and c °P^ a " which are situated along cannot detect elements of the breathing movement 



the medial line of the body. The Mm. levators of fish in it. The external gill concavity thus 



arcuqm branchialium also contract, drawing up- does not participate in the pumping of the water, 



ward the back and posterior regions of the gill In contrast to the condition in fishes the water' 



chambers. As a result, the latter turn and the is not sucked through the gill slits but passes 



hyobranchial disc which is furthermore connected them passively. The two-cycle pump of the larvae 



immoveably with copu l a II is depressed. The of Anura thus works as a one cycle pump in the 



forward region of the ventral wall of the eso- larvae of Urodela. Investigation of the ontogene- 



phagus ,n the tadpoles of Phaneroglossa is con- sis of the higher hyobranchial apparatus in anuran 



nected to the posterior region of the hypobran- larvae permits us to explain the particular fea- 



chial disc. For this reason, the esophagus opens tures of its construction and function which are 



when the hypobranch ial disc is depressed. As a connected with the change in the plane of oscil- 



result of the complex of described motions, the lation. As in the urodelan larvae the mesenchymal 



entire median region of the floor of the oro- formations of the arches of the hyobranchial 



pharyngeal cavity curves upward and the water skeleton are initially positioned in the trans- 



which has poured in through the oral opening verse plane. The same complement of elements of 



