THE EMBRYOLOGY AND ETIOLOGY OF TUMOURS 93
in the form of embryomata, finally of tumours, even of cancer. In this way it comes to be recognized that there must be a vast difference among the various vagrant and aberrant germ-cells in potentialities for mischief. Some few, and not all—how many in each case it is at the moment impossible to say, and it may never be determined—possess the potentiality of developing like the embryo containing them. If they do this normally, identical twins, triplets, etc., may result. If they do not degenerate, and degeneration is probably often their fate, they may come to lie somewhere or other in the embryo, even in its sexual organs. Here they may be encapsulated for a longer or shorter time, and, finally, one or more of them may commence (abnormal) development, and form an embryoma, or other tumour even, by attempting to begin the whole cycle anew, with arrest in the embryonic portion—a cancer.* Vagrant germ-cells in development are, I imagine, far too numerous for anything like all to be required to account for the tumours and for cancer. Probably it may be regarded as sufficient if there be in every development at least one, three, or seven such, which, if they do not degenerate, may become the seed of later tumours. To the embryologist it is of great interest to establish that, as in the upward direction the embryomata pass step by step into identical twins, triplets, etc., so as gradually in the downward one
* It should be mentioned that pure embryomata, as true, benign tumours, are probably in all cases congenital—that is, commencing their development at the same time as the individual harbouring them. Apparently, this does not invariably exclude the appearance of malignancy in some of them at a later time. On the other hand, malignant disease (carcinoma and sarcoma) is not congenital, but the seed of such a tumour is to be found in certain of the latent germ-cells, as described in the text. Of course, cancer is hereditary, no matter what all the official cancerresearchers in the world may say. The true nature of heredity is as far from their thoughts as the principles of modern embryology.