DEVEI-OPMENT OF TEETH IX HATTEEIA PUNCTATA. 211 



lin.gr. Mandibular (internal) dental fossa, man. Mandible, man. lab. Epi- 

 thelial ingrowth labial to mandibular teeth (labio-dental strand), man. lin. 

 Epithelial ingrowth lingual to mandibular teeth, tuax.f. Maxillary tooth of 

 functional series, mes. Mesoderm, mk. Meckel's cartilage, tn. lab. Epi- 

 thelial ingrowth labial to maxillary teeth (labio-deutal strand), m. lin. Epi- 

 thelial ingrowth lingual to maxillary tooth, tn.p. Mesodermal dental papilla. 

 p. lab. Epithelial ingrowth labial to palatine teeth, p. lin. Epithelial in- 

 growth lingual to palatine teeth, pmx. Premaxilla. post. Posterior, r.d.l. 

 Residual dental lamina, st. Stellate tissue of enamel organ, t. s. Successional 

 tooth. 



(Outlines of all sections drawn with camera lucida.) 



ElG. 1. — Section of the enamel organ of a tooth of the first series (first, 

 left, upper), with dental lamina on the lingual side. d.f. Dental furrow. 

 (Embryo Q, 52a. Sagittal section, x 240.) 



Fig. 2. — Section of the second tooth of the first series, which is already 

 well calcified. (From same series of sections as fig. 1. X 240.) 



Fig. 3. — Section througii the enamel organ of the first premaxillary tooth 

 (right), belonging to the future functional series. (Embryo R, 142. Sagittal 

 section. X 240.) 



Pig. 4. — Section through enamel organ of the right anterior palatine tooth, 

 and the sixth maxillary, of the functional series. The small palatine tooth of 

 the first series is seen lying linguully to the palatine, enclosed in epidermis. 

 The epidermal ingrowth labial to maxillary (hibio-dental strand) is just 

 becoming evident. /;. e. o. Enamel organ of palatine tooth of functional series. 

 pal.l. Palatine tootii of first series. (R, 102. Frontal section, x 60.) 



Fig. 5. — Section through left maxillary, palatine, and mandibular dental 

 regions, immediately posterior to first palatine tooth, and through the seventh 

 mandibular. (From same series as Hg. 4. x 60.) 



Fig. 6. — Section through eighth maxillary tooth of right side. This is one 

 of the smaller teeth of the alternating series (cf. fig. 11), and is more 

 advanced than the seventh (cf. fig. 7). (R, 162. Frontal section. X 240.) 



Fig. 7. — Section through seventh maxillary tooth of right side, for com- 

 parison with fig. 6. (R, 162. Frontal section, x 240.) 



Fig. 8. — Section through the eighth mandibular (left). (R — S. Frontal 

 section, x 60.) 



Fig. 9. — Section through right palatine and maxillary teeth to show the 

 relations of the epidermal ingrowths at this stage, pal.f. Palatine tooth of 

 functional series. ma.v. Maxilla. (Embryo R — S. Frontal. X 60.) 



Fig. 10. — View of premaxillary and anterior mandibular teeth at Stage S, 

 from a prepared skull. X 5. 



Fig. 11. — Lateral view of teeth at Stage S, to show the conspicuous alter- 



