Or, in a sphere of the same diameter, 530,000,000,000,000 of the two components. Taking a single mammalian spermatozoon, having a mean diameter of 1/6000 of an inch; "it might contain two and a half million of such gemmules. If these were lost, destroyed, or fully developed at the rate of one in each second, this number would be exhausted in about one month; but since a number of spermatozoa appears to be necessary to produce perfect fertilization, it is quite easy to understand that the number of gemmules introduced into the ovum may be so great that the influence of the male parent may be very marked, even after having been, as regards particular character, apparently dormant for many years." The germinal vesicle of a mammalian ovum being about 1/1000 of an inch, mean diameter, might contain five hundred million of gemmules, which, if used up at the rate of one per second, would last more than seventeen years. If the whole ovum, about 1/150 in diameter, were all gemmules, the number would be sufficient to last, at this rate, one per second for 5,600 years! This, however, is not probable; but Mr. Sorby's remarks has completely removed all doubt as to its physical possibility from the Darwinian theory; "and they prompt us," says Slack, "to a wonderful conception of the powers residing in minute quantities of matter." The laws of inheritance are divisible into two series, conservative and progressive transmission; the laws of adaptation to direct (active) or indirect (potential) adaptation.