TKANSITIONAL LBPIDOMAS 325 



the tumours derived from tissues of direct descent from the 

 epiblast and hypoblast, and the secondary or transitional lepido- 

 mata, which include tissues of indirect descent from the same, 

 and which may as a consequence show what I may term transi- 

 tional characters. Making this division, I leave it open as to 

 whether we speak of the tumours of the first order only as the 

 true carcinomata, and refer to those of the second order as at 

 most carcinomatoid, or speak of all tumours of what I may now 

 without. confusion refer to as having lepidic characters, as being 

 carcinomata. My preference, as I have already stated, is for 

 employing this term purely in a histological sense. 



Eecognizing that many years have passed since I was engaged 

 in the active study of embryology, I have not ventured to publish 

 this paper without consulting those most capable of pronouncing 

 authoritatively upon the embryological problems here involved ; 

 and I would here express my sincere thanks and sense of deep 

 obligation to Professor Charles Sedgwick Minot of Harvard, 

 and Professor Carl Huber of Ann Arbor, for their most kind 

 criticism and suggestions in connexion with the views here 

 elaborated. I very gladly acknowledge also that I owe more 

 particularly to a correspondence with Professor Huber, now 

 some months ago, my recognition of the importance, from a 

 pathological point of view, of distinguishing between the meso- 

 thelial and mesenchymatous derivatives of the mesoblast. 



