INTRODUCTORY NOTE 



THIS volume is based on a course of three 

 lectures on the development of the 

 mammary apparatus of the Mammalia, de- 

 livered at University College in March, 1913, 

 under the auspices of the Board of Studies in 

 Zoology, University of London, by Dr. Ernst 

 Bresslau, at that time Professor of Zoology in 

 the University of Strassburg. The proofs were 

 ready for the press in 1914, but the issue of 

 the volume has been delayed until now, owing 

 to the conditions arising out of the war. 

 This delay in publication, I hasten to add, in 

 no way detracts from the value of the volume. 

 Professor Bresslau is the foremost living 

 authority on the morphology of the mammary 

 organs, and by his detailed and fundamental 

 researches, pursued over a period of some 

 twelve years, he has enormously extended our 

 knowledge of the organogenesis of this char- 

 acteristically Mammalian system, and more 

 particularly of those accessory structures — 

 e.g., the incubatorium, the marsupium, and the 

 nipples — which have been superadded in the 



