136 BIOLOGICAL LECTURES. 



except in cases of actual "hybridity." This use of "conver- 

 gence" is an excellent example of a well-meaning but mistaken 

 attempt to convey new ideas by the use of old terms, since I 

 imagine that the authors using this term never meant to imply 

 that such forms were genetically convergent. 



Any form of diagram or expression that describes organisms 

 as masses or lines radiating in every direction from a center in 

 order to emphasize the fact that many of them are reversions 

 or returns of preexisting forms, can be objected to on the same 

 grounds. Suppose the author of such a diagram or description 

 to be correct, and that his so-called reversions are real rever- 

 sions and not simple parallelisms, nevertheless his reversionary 

 forms sprang necessarily from a given level of time and space, 

 and it is as erroneous as it is unnecessary to represent them 

 by lines or names which are placed below this level. Whatever 

 diagrammatic or descriptive form may be selected it must have 

 a base level in time or space upon which the primal point or 

 points or line or base rests, and below which lines or figures 

 representing genetic stocks should not be drawn. 



The serial nature of all organisms and genetic stocks is also 

 thrown into proper prominence by this view of the phenomena 

 of evolution. All series begin necessarily with an imaginary 

 starting point, to which the series may be traced by its grada- 

 tions, but in which its essential characters do not exist, this 

 being the zero point of that particular series. Such organisms 

 are well known to all phylogenists, animals that would cer- 

 tainly be placed in different series from those to which they 

 are referable through intermediate gradations, if those grada- 

 tions had not been traced. Such forms often give rise to end- 

 less controversy unless they occur associated in the same fauna 

 with the forms into which they grade. Next to this first more 

 or less indefinable beginning comes the simplest unit of the 

 morphic series in which the type is distinctly recognizable. 

 This originates quickly and is followed by a comparatively 

 sudden expansion into a number of distinct and often widely 

 separated forms having very different morphic characters. 

 Thus, the foundations of the various stocks or branches of the 

 phylum are laid by quick processes of evolution, not slowly, as 



