Theories of Evolution 15 



as well as in the collateral branches of the gen- 

 ealogical tree. Sometimes it prevails, and 

 the monocotyledons are obviously a reduced 

 branch of the primitive dicotyledons. In or- 

 chids and aroids, in grasses and sedges, reduc- 

 tion plays a most important part, leaving its 

 traces on the flowers as well as on the embryo of 

 the seed. Many instances could be given to prove 

 that progression and retrogression are the two 

 main principles of evolution at large. Hence 

 the conclusion that our analvsis must dissect the 

 complicated phenomena of evolution so far as 

 to show the separate functions of these two con- 

 trasting principles. Hundreds of steps were 

 needed to evolve the family of the orchids, but 

 the experimenter must take the single steps 

 for the object of his inquiry. He finds that 

 some are progressive and others retrogressive 

 and so his investigation falls under two heads, 

 the origin of progressive characters, and the 

 subsequent loss of the same. Progressive steps 

 are the marks of elementary species, while re- 

 trograde varieties are distinguished by ap- 

 parent losses. They have equal claim to our 

 interest and our study. 



As already stated I propose to deal first with 

 the elementary species and afterwards with the 

 retrograde varieties. I shall try to depict them 

 to you in the first place as they are seen in 



