The Development of the Frog Th 



up into a series of nine vertebra, followed by a posterior 

 unsegmented portion, which later becomes the urostyle. 

 This transverse division does not affect the notochord, 

 which remains as a continuous structure until the 

 complete absorption of the tail at the end of the met- 

 amorphosis. Shortly after the metamorphosis thin rings 



Fig. 27. — DrAGRAMMATIC FIGURE OF THE ARTERIAL SYSTEM OF 

 THE MALE FROG, FROM THE RIGHT SIDE. (After Marshall.) 



a, stomach. ^, nostril, c, small intestine. c«, carotid artery. cff^ 

 carotid gland, cm, coeliaco-mesenteric artery, c «, cutaneous artery, d, large 

 intestine, da, dorsal aorta. _/", femur, h, spleen, ha, hepatic artery. /. 

 right lung, ia, lingual artery, w/, testis, o, kidney, oa, occipito-vertebral 

 artery, pa, pulmonary artery, r, pelvic girdle, j, sternum, sa, subclavian 

 artery, .re, sciatic artery, t, tongue. ia, truncus arteriosus, ua, urino- 

 genital arteries, v, ventricle. I, carotid arch. -2, systemic arch. 3, pulmo- 

 cutaneous arch. 



of bone, slightly constricted in their centres, so as 

 to be hourglass-shaped in section, are developed in the 

 membrane investing the cartilaginous sheath of the 

 notochord : these correspond with the nine vertebras 

 already present, and form the first rudiments of the 

 vertebral centra. In the intervertebral regions, between 

 the successive bony rings, annular thickenings of the 



