XI PHENOMENA OF ORGANIC NATURE 395 



and the pollen-grain, as in the flowering plants, or 

 the ovule and the antherozooid, as in the flower- 

 less. Among all forms of animal life, the sperma- 

 tozoa proceed from the male sex, and the egg is 

 the product of the female. Now, what is remark- 

 able about this mode of reproduction is this, that 

 the egg by itself, or the spermatozoa by themselves, 

 are unable to assume the parental form ; but if 

 they be brought into contact with one another, 

 the effect of the mixture of organic substances 

 proceeding from two sources appears to confer an 

 altogether new vigour to the mixed product. This 

 process is brought about, as we all know, by the 

 sexual intercourse of the two sexes, and is called 

 the act of impregnation. The result of this act 

 on the part of the male and female is, that the 

 formation of a new being is set up in the ovule or 

 egg; this ovule or egg soon begins to be divided 

 and subdivided, and to be fashioned into various 

 complex organs, and eventually to develop into 

 the form of one of its parents, as I explained in 

 the first lecture. These are the processes by 

 which the perpetuation of organic beings is secured. 

 Why there should be the two modes why this 

 re-invigoration should be required on the part of 

 the female element we do not know ; but it is most 

 assuredly the fact, and it is presumable, that, how- 

 ever long the process of non-sexual multiplication 

 could be continued I say there is good reason to 

 believe that it would come to an end if a new 



