SKELETON OF COMMON FROG. 



79 



Heart, vessels, carotid gland. Boas, M. J. vii. 1881, p. 488; cf. especially 

 pp. 502 and 540; M. J. viii. 1882. Sabatier, Eludes sur le Coeur, &c., Paris, 1873 ; 

 Fritsch, Archiv. f. Anat. und Physiol. 1869. 



Spleen. Phisalix, A. Z. Expt. (2) iii. 1885. 



Lymphatic system. Langer, SB. Akad. Wien. viii. Abth. i. 1866; iv. Abth. i." 

 1867. 



Urogenital system. Spengel, Arb. Zool. Zoot. Inst, Wurzburg, iii. 1876. Con- 

 nections of nephrostomata. Nussbaum, Z. A. iii. 1880. 



Spermatogenesis. Blomfield, Q. J. M. xxi. 1881. Albumen glands of Oviduct. 

 Loos, Z. W. Z. xxxv. 1 88 1. 



15. SKELETON OF COMMON FROG (Rana temporaria\ 



With Figures 6 and 7. 



THE skeleton, as is commonly the case in Amphibia, retains a large 

 amount of cartilage, in the deeper portions of which much calcareous matter 

 is deposited, but not in the form of bone. 



P.F. P..S 



PrO 



En. 



PMx. 



Mck. 



se.k 



Eti. 



FIG. 6. FIG. 7. 



After Professor W. Kitchen Parker. The cartilage is dotted ; the cartilage bones are shaded 

 with oblique lines, and the membrane bones left white. The lettering is explained in the text. 



The skull is remarkably flat, and the cranium proper of small size, 

 though the total breadth is great owing to the large size of the orbital 

 fossae. Its parts may be readily identified with the help of Figs. 6 and 7. 

 There are two condyles (O. .) formed by the two exoccipitals (E. O.} which 

 are pierced each by a foramen for the vagus nerve (X}. The otic capsules 

 project laterally but contain only one ossification, the pro-otic (Pr. O.) 

 which is pierced by the fifth nerve ( V}. The cranium in front of the otic 

 capsules is cartilaginous and the cartilage is pierced by the optic nerve (//), 

 but most anteriorly of all it contains a bone, the girdle bone, os en ceinture, 

 or sphen-ethmoid (Sp. Et.}. This bone has an internal vertical septum. 

 On the upper surface of the cranium lie the fronto-parietals (P.F^): on its 



