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this is not to be positively asserted, because the inactivity of these 

 properties may be explained by a peculiar state of combination, 

 which it may be one effect of fecundation to dissolve. 



10. If the properties contained in the maternal ovum and 

 those of the cause of fecundation were precisely the same, it is 

 obvious that no change, save that of increment, could result from 

 their combination. But other changes do result from it, and those 

 of the most complicated kind: it is therefore equally obvious that 

 a condition of these rudiments takes place upon their union, 

 which was not previous to their union, and that this process is 

 one of causation, which has been said to be the combination of 

 differentials; or, in other words, something is supplied to the 

 ovum which it wanted, to commence the processes which end in 

 foetal life; and something is supplied by the ovum to the seminal 

 matter, which it wanted in order to commence the same processes, 

 these, singly, not being constituted for such an end. 



11. Thus then we see that in order to exhibit the state of 

 feetal life, at which period, and subsequently, the resemblance of 

 properties to those of the parent is also exhibited, it is necessary 

 that something different should mutually be supplied. Whether 

 this difference, this process of constitution, belongs to all the 

 parts of the spirit, or only to some of them, is a question to be 

 examined. 



12. As the offspring from ^ male and female, of varieties of 

 a species, is found to be modified in all its parts; as the develop- 

 ment of the bones, &c. in the mule, is not the same as either in 

 the horse or in the ass; as every difference in the progenitors is 

 expressed by a corresponding difference or modification in the 

 offspring; and as progressive causation in a body which is not 

 exposed to adequate external causes, consists only in the develop- 

 ment or changes of combinations of properties already possessed, 

 or latent; so we must conclude that the procreative rudiments on 

 either side contain all the properties of their originals; and that 

 as the offspring affords evidence of the possession of no other pro- 

 perties, but those which do agree with those of the originals, so 

 we must consider the change which occurs in the ovum, sub coilu, 

 as the effect of the combination of the differentials, which in every 

 ease appear to a greater or lesser extent in the progenitors. 



13. It is then that process of constitution which takes place 

 in the ovum by the mixture of the properties of its organic spirit 

 with those of the male, which gives activity to the former, and 

 makes them commence the processes which terminate in foetal 

 life. But whether all the differentials concur in this effect, or 

 whether the activity of the ovum is produced only by a relation of 

 agency subsisting between the properties agreeing in either sex 

 with the generative organs (which are perhaps the only fixed and 

 constant differentials), is a point which cannot be decided, because 

 the difference is not confined to these organs, but might pervade 

 (irregularly, in the several examples) all parts of the constitutions* 

 respectively, of the male and female. 



