626 



that from the study of the caudal pharyngeal complex in its relations 

 to the growth transformations of the rest of the pharynx, in 52 human 

 embryos : — 



(a) No reason is seen for considering the ultimobranchial body, 

 so-called, — either as representing an ancestral gland, vestigial in mam- 

 mals, or 



(b) representing any specific pouch, V or VI, but merely 



(c) formed by a continued growth activity in the branchial 

 entoderm. 



(d) In the mechanics of growth, by the shiftings that occur, the 

 caudal portion becomes fused with the thyroid. 



(e) At this stage, its epithelial syncytium rapidly undergoes a 

 reticulation. 



(f) It is at first clearly circumscribed within the expanding thyroid. 



(g) It soon however becomes indistinguishable and apparently 

 finally in man, disappears (typically) without trace. 



(h) A study of its morphology gives no suggestion of a specific 

 function, either past or present, that may be ascribed to this pharyngeal 

 derivative. 



List of Papers referred to. 



VON Bemmeln, 1889. Ueber die Suprapericardialkörper. Anat. Anz. Vol. 4, 

 pp. 400—407. 



Bremer, J. L., 1905. Description of a 4 mm. Human Embryo. Amer. Jouro. 

 of Anat. Vol. 5, pp. 459-480. 



BcxTON, B. H., 1899. Photographs of a series of sections of an early human 

 embryo. Journ. of Anat. and Physiol. Vol. 33, pp. 381 — 385. 



Elze, Curt, 1907. Beschreibung eines menschlichen Embryo von zirka 7 mm. 

 größter Länge unter besonderer Berücksichtigung der Frage nach der Ent- 

 wickelung der Extremitätenarterien und nach der morphologischen Bedeu- 

 tung der lateralen Schilddrüsenanlage. Anat. Hefte Vol. 35, pp. 409—492. 



Greil, A., 1905. Ueber die Anlage der Lungen, sowie der ultimobranchialen 

 (postbranchialeu, suprapericardialenl Körper bei anuren Amphibien. Anat. 

 Hefte Vol. 29, pp. 445-506. 



Grosser, O., 1910. Zur Kenntnis des ultimobranchialen Körpers beim Menschen. 

 Anat. Anz. Vol. 37, pp. 337—342. 



Grosser, 0., 1911. Die Entwicklung des Kiemendarms und des Ilespirations- 

 apparates. In: Handbuch der Entwicklungsgeschichte des Menschen, 

 herausgegeben von F. Keibel und P. P. Mall, Vol. 2, pp. 436—482. 



Hammar, J. A., 1901. Studien über die Entwicklung des Vorderarmes und 

 einiger angrenzenden Organe. I. Abteilung: Allgemeine Morphologie der 

 Schlundspalten beim Menschen. Entwicklung des Mittel ohrraumes und 

 des äußeren Gehörganges. Arch. f. mikr. A.nat. Vol. 59, pp. 471 — 628. 



