110 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



Lingua and Superlinguae. 



Not until Stage 3 are the fundaments of the superlinguoe (" para- 

 glossie" of some authors) observed ; then a ventral aspect of the germ 

 band (Plate 3, Figure 11) reveals two small papillse (siting.) between 

 the mandibles with their centres slightly more anterior than those of 

 the mandibles. Although each small papilla is adjacent or contiguous 

 to the mandibular fundament of the same side, it originates quite inde- 

 pendently ; in other words, it is not the inner branch of a biramous ap- 

 pendage, but a distinct ectodermal evagination, as transections of the 

 germ band (Plate 4, Figure 23, su'lng.) prove. 



At Stage 4 (Plate 3, Fig. 12, siClng.) the superlingual fundaments 

 are longer and stouter than before, and have moved back slightly in re- 

 lation to the mandibles until nearly opposite them. 



At Stage 5 the centres of the superlinguae (Plate 3, Figure 21, sii' Ing.) 

 are behind those of the mandibles, and in cross-sections (Plate 4, Figure 

 23) the former structures are seen to have exceeded the latter in rate 

 of elongation. The long axes of the superlinguce now diverge anteriorly 

 from the median plane and the apices are partly under the mandibles, 

 as in the adult, though the bases retain nearly their original positions in 

 relation to the bases of the mandibles. During this stage is seen the 

 first trace of the lingua (the " ligula," or " hypopharynx " of some 

 authors), as a slight, median, unpaired, oval, ectodermal evagination 

 (Plate 3, Figure 21, Ing.) between the first maxillae. This is the last of 

 the oral fundaments to make its appearance. 



In Stages 6 and 7 the lingua becomes longer and stouter, and, as 

 seen in a ventral view of the germ band (Plate 5, Figure 30, Ing.), its 

 cross-section is rounded-triangular with its anterior median angle intrud- 

 ing between the two superlingufe. Sections show that the lingua and 

 superlinguje have swung forward from their former positions at right 

 angles to the germ band, and that the lingual and superlingual cavities 

 are separately confluent with the general body cavity of the head. In 

 the region of confluence a common cavity — a prolongation of the body 

 cavity — is formed by a median evagination of the germ band itself. 

 In Apterygota the superlinguae, however, never become appendages of 

 the lingua. 



In ventral aspect, the lingua at Stage 7 (Plate 4, Figure 27 ; Plate 5, 

 Figure 29) is cuneate with rounded apex, and, a little later (Plate 4, 

 Fi'^'ure 25, Ing.) becomes constricted distally, forming a terminal lobe. 

 In Stage 8 the lateral surfaces (Plato 5, Figure 34) become concave. 



