BY R. BROOM. 727 



will be noticed, as exemplified by the measurements of the leg, 

 foot, and tail. 



The two embryos shown in Plate xxv., illustrate the later devel- 

 opment of the mammary foetuses. The most striking feature 

 here shown is the rapid growth of the hind limbs and tail. 

 Another point that will be noticed is the change of attitude of 

 the pinna of the ear. In all the early embryos it is directed 

 forwards, but shortly after it becomes free from the epitrichial 

 layer it increases greatly in size, and becoming somewhat more 

 ilexible it, as a rule, becomes folded backwards. Though this is 

 the casein the large majority of embryos, occasionally the ears 

 continue to be directed forwards till a late stage in development. 

 In the large embryo shown in fig. 14 the right ear is folded back, 

 while the left is still directed forwards. 



In the smaller of the two late mammary foetuses shown in fig. 

 13, hair is to be found practically all o\'er the body. The hair, 

 however, is scarcely longer, nor are the hairs more closely together 

 than in the earlier embryos, so that the body still looks, at first 

 sight, quite naked. The vibrissas are of large size, and the 

 enlarged hairs above and below the orbits are also well developed. 

 The wrist enlarged hairs and those under the lower jaw are also 

 showing, but the ankle hairs are not yet through the surface. 

 The claws on the two outer toes of the hind feet are of large size, 

 those of the syndactylous toes small but well formed, while the 

 little claw of the hallux, instead of being more developed, is rather 

 less marked than in some of the earlier stasfes. The following- 

 are the principal measurements at this stage: — Head, 23-5 mm.; 

 snout to tail, 99 mm.; tail, 30 5 mm.; ai-m, 24-5 mm.; leg, 23 5 

 mm.; foot, 10-5 mm. 



The embryo shown in fig. 14, with the exception of its being- 

 still scantily clad with hairs differs but little in its character 

 from the adult. The eyelids, though still closed, may be said to 

 be fully formed, and the lips, though they are still closely 

 cemented except in front, as indeed they are till a much later 

 period, can be ]>ulled apart without apparent injury. This 

 embryo is a female. There is a deep pouch, and the clitoris is still 



