BY R. BROOM. 723' 



is performed by the Wolffian bodies. The true kidney is 

 developed much in advance of the condition in Embryo F, though 

 still much too imperfect to be functional. The upper end of the 

 kidney is almost on a level with the top of the Wolffian body, 

 and on the right side is practically in contact with the liver. 

 The Muellerain duct can be traced for nearly half a millimetre. 

 The suprarenal bodies are of large size. The genital glands are 

 of considerable size, and the sex may possibly be differentiated, 

 but I should like to examine more than one embryo of this stage, 

 and some later specimens in which the sex is undoubtedly defined 

 before being sure on this point. 



In describing this and the earlier embryos there are one 

 or two points which I have refrained from dealing with, such as 

 the mammary glands, thymus, thyroid, etc., as a further examina- 

 tion will require to be made of later stages before the early con- 

 dition of the mammary glands can be satisfactorily understood ; 

 and though the earliest embi'yos here described show the thymus 

 and thyroid in very interesting conditions, still earlier specimens 

 will be required to show their modes of develoj)ment. 



Later Mammary Foetuses. 



With the limited time at my disposal it is practicallj^ impossible 

 for me at present to follow the later development of the various 

 organs throughout the developing mammary foetuses ; but as 

 opportunity offers the developmental history of certain structures 

 will be fully traced. At present I am engaged in working out the 

 development of the shoulder girdle and of the skull, and trust 

 shortly to be in a position to give an account of the development 

 of the mammar}' glands and pouch. As many of the post-natal 

 stages will be used in future woi'k, and as there is much of interest 

 in the external anatomy, I have thought it well to give a 

 description of a number of typical examples of the smaller 

 mammary foetuses. 



The most noticeable change that takes place in the embr3"o 

 shortly after birth is a considerable increase in size of the abdo- 

 minal region. This is doubtless due to the greater development 



