BY R. BROOM. 721 



Epichrmis. — The epitrichial la_yei' is moderately thick all o\er 

 the body; but, as in the previous embryo, the layer is thickest on 

 the head and fore limbs. The hair follicles of the large hairs of 

 the head and fore limbs are well formed, but there is no trace as 

 yet of the follicles of the body hairs. The claws of the digits of 

 the anterior limbs are well formed, but on the posterior digits, 

 though the epithelium is thickened at the tips, there is no distinct 

 evidence of claws. The anterior dental germs are well formed, 

 and the dental lamina can be traced well back. 



Sk^leliin. — The cartilaginous skeleton is almost complete. The 

 vertebral centra are chondrified well into the tail, and in the 

 upper vertebral region the notochord is almost obliterated except 

 in the inter-vertebral discs. The neural arches do not yet meet, 

 however. The upper limb is completely formed, and the cora- 

 coid well chondrified to its attachment with the sternum. The 

 lower limb is almost completely formed, the phalanges and the 

 tarsal elements being chondrified. The chondrocranium may be 

 regarded as complete, and the following bones are well ossified — 

 premaxillaries, maxillaries, palatines, pterygoids and mandibles. 



Nervous si/stem. — The brain is taking on the adult characters. 

 The choroid folds into the lateral ventricle, is partly formed, and 

 the paraphysis well marked. Though the corpus striatum and 

 optic thalamus can be detected, they are not as yet well formed- 

 The spinal cord on section is almost round. The central canal is 

 still very large, and on section somewhat club-shaped. The 

 cellular elements are much more numerous round the posterior 

 half than on anterior; the anterior grey columns are, however, 

 larger than the posterior, so that the whole grey matter of the 

 cord becomes on section almost round. The anterior and posterior 

 white columns are both fairly well formed, but contribute still 

 further to giving the cord a I'ounded appearance. There is as yet 

 no trace of a posterior fissure. 



>)iense organs. — The nose is well formed, though the turbinals 

 are as yet but imperfectly formed. Jacobson's organ is well 

 formed, and is typically marsupial in character. The eye is still 

 imperfectly formed. The la3^ers of the retina are not yet 



