Fepruary, 1908. | THE ORCHID REVIEW. 59 
are called “ Mendelian pairs.” One unit of a Mendelian pair is held to be 
dominant over the other, hence the terms ‘“‘ dominant ’”’ and “ recessive” 
characters. 
More recently it has been held that the presence and absence of a 
character may constitute the two halves of a Mendelian pair—thus “ purple” 
and “ non-purple ”—‘“ presence being dominant over absence, which a friend 
waggishly remarked reads like something out of ‘Alice in Wonderland.’”’ 
Even sex has been claimed as a Mendelian character. 
Mendel’s discovery has been described as of far-reaching importance— 
indeed it has been tersely put that ‘the biological problem of the future 
will be not so much the origin of species as the origin of unit characters.” 
This is elevating Mendelism to the rank of an all-embracing theory of 
hereditary besides which other questions sink into significance. 
But is there not another explanation of the phenomena included under 
the term Mendelism ? Enormous progress has been made in hybridisation 
since Mendel carried out his original experiments, and every hybridist is 
familiar with what may be termed the dissociation of specific characters in 
secondary hybrids. But something far deeper than this is required. We 
want to know the relationship of Mendelism to the opposing forces of here- 
ditary and evolution—the tendency of organisms to adapt themselves to 
changing circumstances and the tendency to remain constant. What 
are the forces which have led to the marvellous complexity of 
character seen insuch an Orchid as Cycnoches Egertonianum (0.R. xv. 
pp- 337-340, fig. 37)? And what are the successive changes by which this 
complexity has been reached? A correct answer would embrace a real 
theory of heredity, but it is one which in my opinion Mendelism is no 
competent to give. 
What is a species? And why does it remain constant during long 
periods of time? Why does it reproduce itself true, either from seed or 
otherwise, without those perplexing eccentricities seen in the hybrids and 
garden races which are so much the subject of Mendelian experiment ? 
Why are “‘ Mendelian characters ” not universal ? And one more query—if 
I have not exhausted the printer’s stock—Why is it that two species of 
normal and constant behaviour when breeding pure—or two albinos, for the 
matter of that—behave so differently and erratically when intercrossed? The 
answer is that the difference lies in their past history and their relationship 
to each other. 
Species are adaptational forms which have arisen under the influence of 
natural selection, the individuals of which are capable of handing on their 
essential characters to their descondents. Though fixed in character, they 
are not immutable, but are subject to the operations of the same laws that 
gave them birth. They fluctuate under varying conditions, and if such 
