58 THE ENZYME TREATMENT OF CANCER
animals
or vertebrates. But the numbers appeared to work out to the same (about 128) in
both (potentially) male and female embryos of the above two dog-fishes. I was
sure in my own mind that the real number in potentially female embryos of each
was not 128, but 256. This was the position when, in 1903, the writer was
compelled to lay aside his germ-cell researches, in order to undertake a
campaign against cancer. Owing to this, the publication of the series of
germ-cell memoirs was interrupted, for no time could le found to extend the
tedious countings of germ-cells in embryos of these two dog-fishes. This task
was afterwards undertaken on my material by an able amateur
microscopist—my friend W. T. Haydon, an engineer, of Liverpool. His finds
showed clearly that my Suspicions were well founded, for it turned out that in
these fishes, as in the skate, the approximate number of primary germ-cells in
potential female embryos was at one time in the development double that in the
male, being 256 against 128 in the male. Later on the numbers became equal in
the two sexes, owing to this degeneration of one of the ovaries.
The
number of Elasmobranch embryos hitherto examined is several hundred, belonging
to different species, and in all these under a certain age no single embryo has
been seen, in which all the germ-cells present might he described as normally
placed. The percentage of vagrant germ-cells varies ; it is usually from 10 to
12 per cent. in Pristiurus, and from 25 to 30 per cent. in Raja
batis. The places where these occur are numerous: in the body cavity, upon
the splanchnic (gut) mesoblast, on the sub-intestinal veins, in kidney tubules,
in the pericardium, in the liver, in the skin, in any part of the gut
epithelium, especially in the rectum, rarely in the head or gill region, and
practically always there are some in the immediate