I.] GENESIS OF DIFFERENCES. 19 



The gametophytic generation is associated with the act 

 of fertilization, tlie male prothalhis or gametopliyte de- 

 veloping from the pollen grain and soon perishing, and 

 the female prothallus or gametophyte developing in 

 the ovule, and either soon perishing, or persisting, at 

 least in the conifer -like plants, in the form of the 

 albumen of the seed. The great development of the 

 sporophyte in later time is, no doubt, a consequence of 

 the necessity of assuming a terrestial life ; and with 

 this development has come the perfection of centro- 

 genetic form. 



n. 



The Origin of Differences. 



The causes which have contributed to the origin of 

 the differences which we see in the organic creation have 

 been and still are the subjects of the most violent con- 

 troversy. Those persons who conceive these differences 

 to have come into existence full -formed, as they exist at 

 the present time, are those who believe in the dogma of 

 special creations, and they usually add to the doctrine a 

 belief in design in nature. This doctrine of special cre- 

 ation receives its strongest support when persons con- 

 trast individual objects in nature. Certainly nothing 

 can seem more unlike in .very fundamental character 

 than an insect and an elephant, a star fish and a potato, 

 a man and an oak tree. The moment one comes to 

 study the genealogies of these objects or groups, how- 

 ever, he comes upon the astonishing fact that the an- 

 cestors are more and more alike the farther back they 

 are traced. In other words, there are great series of 



