136 Darwin, and after Darwin. 



I have dealt thus at considerable length upon the 

 processes whereby the originally unicellular ovum and 

 spermatozoon become converted into the multicellular 

 germ, because I do not know of any other exposition 

 of the argument from Embryology where this, the first 

 stage of the argument, has been adequately treated. 

 Yet it is evident that the fact of all the processes 

 above described being so similar in the case of sexual 

 (or metazoal) reproduction among the innumerable or- 

 ganisms where it occurs, constitutes in itself a strong 

 argument in favour of evolution. For the mechanism 

 of fertilization, and all the processes which even thus 

 far we have seen to follow therefrom, are hereby 

 shown to be not only highly complex, but likewise 

 highly specialized. Therefore, the remarkable simi- 

 larity which they present throughout the whole animal 

 kingdom not to speak of the vegetable is expressive 

 of organic continuity, rather than of absolute dis- 

 continuity in every case, as the theory of special 

 creation must necessarily suppose. And it is evident 

 that this argument is strong in proportion to the 

 uniformity, the specialization, and the complexity of 

 the processes in question. 



Having occupied so much space with supplying what 

 appear to me the deficiencies in previous expositions 

 of the argument from Embryology, I can now afford 

 to take only a very general view of the more important 

 features of this argument as they are successively fur- 

 nished by all the later stages of individual development. 

 But this is of little consequence, seeing that from the 

 point at which we have now arrived previous exposi- 

 tions of the argument are both good and numerous. 

 The following then is to be regarded as a mere sketch 



