Charles Eussell Bardeen and Warren Harmon Lewis 5 



entli to the eleventh myotomes. It is, therefore, probable that two 

 occipital myotomes are present. But nine myotomes lie in the area 

 between the arm-bud and the leg-bud. The base of the latter lies 

 opposite 31st to the 25th or 86th myotomes. If two myotomes be 

 considered occipital myotomes, the leg, in this instance, lies two seg- 

 ments nearer the head than usual. It is therefore probable that this 

 embryo has an unusually short body-wall. 



Embryo LXXVI (length, 4.5 mm.; age, about three weeks) is of 

 essentially the same stage of development as CXLVTII. It has thirty- 

 five myotomes (3o, 8c, 13t, 51, 5s, 2c). The base of the arm lies 

 opposite the eighth (fifth cervical) to the twelfth (first thoracic) myo- 

 tomes. The base of the leg lies opposite the twenty-fourth (first lumbar) 

 to the twenty-ninth (first sacral) myotomes. Eleven myotomes lie 

 between the regions of the arm and leg-buds. In CXLVIII the limb- 

 buds protrude more than in LXXVI and the body-wall extends further 

 ventrally. 



Embryo LXXX (length, 5 mm.; age, about three weeks), a photo- 

 graph of which is given in Plate I, is similar, though slightly more 

 advanced in development than Embryo CXLVIII. 



Embryo 



In Fig. 4 is represented the His embryo a ; length, neck-breach, 4 

 mm.; age, about 23 days. The back of this embryo is very greatly 

 flexed. Thirty-five myotomes are present (8c, 12t, 51, 5s, 5c). The arpa- 

 bud lies opposite the 5th to 8th cervical and 1st thoracic myotomes; the 

 leg-bud opposite the 1st to 5th lumbar and 1st sacral myotomes. Both 

 protrude further than in CXLVIII. The arm-bud projects in a caudal 

 direction. The leg is represented, not as in the original His drawing, 

 but instead in the more normal position shown in the His drawing of 

 the right side of the same embryo. 



Embryo R. 



In Fig. 5 is represented the His embryo E; length, 5 mm.; age, about 

 3^ weeks. Thirty-five myotomes are pictured (8c, 12t, 51, 5s, 5c). The 

 arm-bud lies opposite the 5th to 8th cervical and 1st thoracic myotomes; 

 the leg-bud opposite the 1st to 5th lumbar and 1st sacral. Both point 

 somewhat caudally. 



Embryo II. 



In Fig. G is represented Embryo II; length, neck-breach, 7 mm.; 

 vertex-breach, 6 mm.; age, about 4 weeks. Thirty-eight myotomes are 



