672 JOHN BEARD, 



mystery, as soon as the occasional presence of primary germ-cells during 

 embryonic life in these very places, among others, is recorded. 



Almost any part of the body may be "infected" by vagrant germ- 

 cells, and in almost every part of the body dermoids may arise. As 

 ah-eady recorded, the skin is especially to be named as a place, where 

 vagrant germ-cells may be encountered. Very often dermoids are 

 connected with the skin, as though it were the matrix of their 

 formation. 



My conclusion, therefore, is, that some of Wilms' embryomas may 

 be represented by dermoids in parts of the body other than the sexual 

 organs. At the same time for the present I accept his judgment, that 

 many of such dermoids are not of the same nature as the embryomas. 



The embryomas are, at the basis, cases of like-twins with one 

 abnormal embryo. The circumstance, that sometimes they may first 

 manifest themselves in adult life, or in old age, does not affect this. 

 An embryoma, at whatever period it appear, is an instance of the 

 development of an additional primary germ-cell , which in all its 

 hereditary characters is the exact counterpart of that primary germ- 

 cell, by whose unfolding the individual harbouring the "dermoid" 

 arose. 



Xni. The Degeneration of certain Grerm-Cells. 



It is unfortunately too true, that embryologists seldom trouble 

 themselves to describe any retrogressive phenomena they encounter. 

 There are notable exceptions; but, were these more numerous, our 

 knowledge of development would be proportionately increased. 



"Das Vergehen" is quite as important a factor in any life-history 

 as "das Werden" ! 



The accident of circumstances has in the course of the last 12 

 years brought more than one example of degeneration in development 

 prominently under the writer's notice. Transient ganglion-cells were 

 followed through all the phases of their atrophy; merocytes of the 

 yolk were traced to their death and extinction. My previous work, 

 therefore, was bound to raise the question of the persistence or non- 

 persistence of the abnormally placed germ-cells, if nothing else did. 



With as an absolute fact, not to be gainsaid or brushed aside, 

 that of the presence of 155 germ-cells in utterly impossible situations 

 in a single embryo of 32 mm, the question "what becomes of these ?" 

 hardly needs raising. It forces itself into prominence. 



It must be owned, that so far the success in tracing the de- 

 generation of the transient ganglion-cells and merocytes has not re- 



