SIGNIFICANCE OF PRIMARY-PRIMOKDIA 35 



pouches or incubatorium— as nearly all writers 

 since Darwin presumed, but much earlier, with 

 the structures I have termed the primary- 

 primordia. The answer to the question as to 

 the origin of the mammary apparatus depends 

 therefore essentially upon the phylogenetic 

 significance we attach to these formations. 



I may perhaps state here that almost a year 

 elapsed between the time when I succeeded in 

 discovering the primary-primordia and that 

 later period when I began to have clearer views 

 as to their significance. During this interval I 

 thought constantly about this question before 

 deciding to develop the theory, which I now 

 wish to place before you. I say this because 

 I am now passing from the domain of fact to 

 the domain of speculation. 



In weighing the question of the significance 

 of the primary-primordia, the first thing to be 

 considered was, whether from a phylogenetic 

 point of view they were not simply indifferent 

 formations, which had no further meaning 

 than that of providing the material for the 

 gland areas in earlier stages of development — 

 that is to say, whether they had any phylo- 

 genetic importance at all. 



