BY R. BROOM. 719 



right vein is practically lost, though it can still be detected as an 

 exceedingly minute vessel. 



Lungs. — In the earlier embryos the bronchial tubes ajDpear as 

 moderately simple tubular processes, but at this stage the terminal 

 tubules have become enlarged into irregular saccular dilatations, 

 along the borders of which further budding is taking place into 

 the mesoblastic tissue. 



Alimentary canal. — The oesophagus is very well formed, and 

 has a moderately wide lumen throughout its whole extent. The 

 rest of tho canal resembles closely that in Embryo E. The 

 stomach and upper part of the small intestine are better developed, 

 and the caecum is larger and more dilated. 



Urinogenital system. — The mesonephros is not much larger 

 than in Embryo E, nor are the tubules more convoluted. The 

 Muellerian ducts are, however, considerably further developed, 

 and the permanent kidney is much advanced, the uriniferous 

 tubules becoming distinctly developed. The genital gland is 

 fairl}^ large, but it has apparently not yet become sexually 

 differentiated. 



Embryo G (14 mm). Plate xxiii., fig. 6. 



This beautifully preserved embryo, though of similar size to the 

 preceding, and quite ready to be born, differs in one or two 

 points. The head is lifted up from the chest and is in a similar 

 attitude to that in the newly born embryo. Though this 

 specimen was removed from the uterus and has the membranes 

 still attached, it has in all probability breathed, and the tip of 

 the tongue is hollowed, as if endeavours had been made to grasp 

 the expected nipple. The fore limbs no longer cross in front of 

 the chest, but hang down as if ready to catch on to the mamma. 

 The hind limbs come well forward and are well developed, the 

 different digits being well shown. The body is considerably 

 larger than in Embryo F, which I think due to this embryo's 

 having breathed. There is one interesting point about this speci- 

 men, in that the epitrichial layer has not quite completely 



