Analysis of Hetbeogeneitt in Complex Chaeactees 343 



From time to time materials were taken from each of the colonies to Chicago, 

 and there tested experimentally to determiae the heritability of the pattern 

 and the gametic constitution of individuals showing it. Pure races of different 

 patterns were obtained, and these, after testing and analysis, gave a good basis 

 for the interpretation of conditions found in nature. 



COMPOSITION OF THE COMPLEX PATTERN. 



An abundance of instances of complex patterns or parts have been recorded 

 and arranged ia a system, a common practice in studies where phylogeny is the 

 basis of arrangement and perspective is limited to some system of phylogeny and 

 hypothesis of evolution. It is here attempted to unravel the intricacies of the 

 complex pattern of the pronotum of these beetles in the effort to discover the 

 laws governing the obvious heterogeneity. It has been shown (fig. 34) that in 

 L. multitceniata there are many patterns giving seeming diversity, and that these 

 can be arranged iu 13 series (fig. 35) ; and further, that these 13 biotype groups 

 of true-breeding types can be further combined iuto a pattern or scheme express- 

 ing the whole range of diversity in the entire species (fig. 36), and upon such a 

 scheme could be graphically represented the variations of the species in any 

 particular location and generation. 



One conspicuous fact of this arrangement is the divergence from biotype type 

 7, through types 4, 3, 3, and 1 to a totally black surface, through types 9, 10, 11, 

 and 12 towards a different extreme, and through 5, 6, and 8 towards still other 

 divergent types. In any population there is evident a complete gradation along 

 any of these lines towards the extreme type, and perfectly continuous series in 

 some of them are at all times evident. The first question to be decided was, is 

 this population a unit with a complete gradation towards some race extreme, or 

 is the population a composite of lesser types which, assembled, produce the 

 scheme of the whole and its apparent " continuous variations " ? 



I had found much earlier that the simpler population of L. decemlineata could 

 be broken up into several lesser groups, depending upon the characters used and 

 the degree of rigorous inbreeding practice. Were these groups natural or arti- 

 ficial ? The work of Johannsen and De Vries raises this question in more urgent 

 form. De Vries postulates " elementary species," and such divisions are found 

 in this species, while Johannsen postulates lesser lines, biotypes, genotypes, and 

 clones, of which biotypes only are found in sexually reproducing species. This 

 material has afforded an opportunity to put to a test some of the recent develop- 

 ments in genetics. 



A postulate common to the conceptions of De Vries, Johannsen, and all of the 

 neo-Mendelian workers is belief in the inability of a minor strain, when pure, to 

 be modified by continued selection of the extremes of its fluctuations. The 

 problems are: (1) can races breeding true without constant selection be 

 obtained ; (3) when obtained, can these be modified by the selection of extremes ? 



One of the most striking characteristics of this material is that when obtained 

 in nature it rarely breeds true with respect to a specific type of pronotal pattern, 

 and usually from a pair of wild parents different types appear in the progeny. A 

 priori, this may be due to wide " variation," or hybrid constitution of the par- 

 ents respecting the types of pattern represented. Breeding will show accurately 

 which one of the two is correct. 



