STAGE 56 Age +/- 38 d.; length 70-100 mm.

Ext. Crit.: *Elbow and wrist clearly indicated; length of free parts of fingers 3 to 4 x their breadth*. *Length of cartilages of 4^th and 5^th toe about 6 x their breadth*.

Int. Crit.: "Stirnorgan" shifted to position just caudal to fused olfactory bulbs. *In descendence of lumbar ganglia, root of gangl. 8 overlapping part of gangl. 7, and root of gangl. 9 of all gangl. 8*. *Olfactory organ divided into two portions*; anlagen of glandula oralis interna and nasolachrymal duct formed. Ventro-lateral love of saccus endolymphaticus extending caudad down to 3^rd spinal nerve, dorso-lateral lobe extending craniad up to diencephalon.

Frontoparietalia fused. *12^th pair of vertebral arches chondrified; chondrification of the dorsal perichordal tube extending vertebrally down to 9^th vertebra and intervertebrally down to 5^th vertebra; beginning of ossification of vertebral portions of perichordal tube; beginning of chondrification of hypochord; *2^nd pair of ribs beginning to chondrify*. *Coracoid slightly ossified perichordally, scapula, procoracoid and coracoid chondrified*. *Chondrification of forelimb up to phalanges, which are still blastematous; ossification extended to forearm*. Shoulder girdle musculature differentiated except for origins and insertions. Greater part of forelimb musculature still in myoblast stage. Perichondral ossification of iliac processes. *Skeleton of hindlimb completely chondrified, ossification extended distally to tibiale and fibulare*. Anlage of ostium tubae indicated. Cavity forming in middle ear anlage. *Urinary bladder forming distinct pocket on ventral side of cloaca*.