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stated, in perfect ignorance; although numerous most interesting facts have been collected regard- ing the circumstances of the begetting; such as the relative condition of the parents, regarded as the two factors; their relative ages; the equality of their potency in regard to the production of sex, or a preponderance on one or other side of a tendency to produce males or females (in some cases so remarkable as to take the matter entirely out of the category of so-called chance or accident); the tendency, again, to the prevalence of a single sex in quadruple or quintuple births, and the almost constant occurrence of the same sex in duplex monsters. These are matters which may ultimately lead to a better understanding of the whole question; while, at the same time, they serve to show how little is as yet known beyond the bare ascertainment of these and similar facts. Before I conclude, I will refer to one other sub- ject, to which I have occasionally adverted in the course of this address. Again and again, passages occur in Harvey's work which lead to the conviction that he is in some sense a supporter of the doctrine of 'equi- vocal' or 'spontaneous' generation. And as, when
