ASPECTS ANI) ETIOLOGY OF CARCINOMA 57
of this from the organism, its conversion into a primitive germ-cell, and the consequent formation of primary germ-cells from this. Normally, as already stated, the further development of a primary germ-cell results in an embryo, not in a larva (asexual generation).
Coming now to the primary germ-cells, upon which many observations have been made, it has elsewhere been established that their number is always a member of the geometrical series 2, 4, 8, 16, 32, etc., or 2 to the nth power, where n is one of the numerals 1, 2, 3, 4, 5, 6, etc., and that the greatest number of primary germ-cells in any embryo will be 2n- 1. Thus, the total number in the common dog-fish (Scyllium canicula) is 128; in the male smooth skate (Reja batis), 256 ; in the female, 512 ; and the greatest number in the embryo of one of these 127 (in Scyllium), 255 (in the male skate), and 511 (in the female skate). But for convenience and brevity, dealing with one form only—say, the dog-fish (Pristiurus)—of the 127 primary germ-cells, it never happens that all, or anything like all, reach the normal position—the germinal ridge or nidus. Usually, at the most from 90 to 100 of them arrive here, the remainder being found in all sorts of unusual places, where many of them degenerate.
Here may be inserted a very brief account of some unpublished finds, which for this reason have escaped the attentions of some observers intent upon “ annexation.” Some ten years ago my observations proved to me that in certain dog-fishes (Scyllium and Pristiurus) the single ovary of the adult female arose by the degeneration during development of the left embryonic ovary and the persistence of the right one. There were at the time many indications—even strong evidences—that the find in the female skate of twice as many primary germ-cells as in the male was a general rule for the back-boned