Reactions and Products in Interspecific Crosses 143 



done by either biometric testing, which is time-consuming and expensive for 

 extensive operations, or by minute examination of antennal characters or the 

 elytral punctations. Further, there were not found results or reactions differ- 

 ing in principles. The crossing of the two has shown only the fact that nothing 

 present appeared or was brought out that was hidden, and might have been 

 productive of the complications found in the previous series. 



DISCUSSION OF RESULTS DERIVED IN CROSSING THE SPECIES 

 L. DIVERSA. L. SIGNATICOLLIS, AND L. UNDECIMLINEATA. 



I have presented at some length and in detail the crossing of these species, 

 and out of these experiments, which were begun in 1904 and are by no means 

 terminated, certain positive advances have, I believe, been obtained, in addition 

 to many aids in the analysis of the composition of the constitution of the 

 germinal material. Begun at a time when the furor of enthusiasm resulting 

 from the recovery of Mendel's work was at its height, I purposely took a most 

 uncompromising position, and in every possible manner made effort in this and 

 other materials that I was using to break down the principles. The reason for 

 this was that I believed that if the principles were true, and not another variety 

 of Weismannism, no amount of adverse investigation would alter the findings 

 and might open the way for extensions of the principles in diverse directions. 

 I have no hesitation in saying that I made every effort of which I was capable, 

 aside from biometric messing-up of heterogeneous things and assuming homo- 

 geneous arrays, and disregard for the accuracy of technical operation, to break 

 down in practice the Mendelian reaction in these materials. To this end I 

 made especial efforts after it became increasingly certain that the reactions were 

 in accord with the principles of reaction described by Mendel. 



In all of this I have most positively failed, and not one certain instance have 

 I been able to find that will stand the tests that it has had to undergo in my 

 examination of it. Mendelian enthusiasts will say that the effort was a waste 

 of time and energy, and had far better been employed in adding to the array of 

 cases. I have no interest in added cases, only in principles, their validity and 

 extension. It was further necessary to test fully the role in these forms of this 

 reaction, in which other operations directed at the problems of evolution were 

 being carried on. 



Current neo-Mendelian conception and terminology characterized the opera- 

 tions in the gametes productive of the differences and arrays that result as due 

 to the " segregation " of factors and determiners, that all too often are conceived 

 of as " carriers of characters," or as " specific nuclear substances," the char- 

 acters being isolated units, compared to blocks in a wall, the entire terminology 

 and conceptions in general being modified Weismannism. The experiences 

 with these crosses of natural species shows that there is no general shifting of 

 characters or units of any sort, either as agents or as conditioning entities. In 

 all it is seen clearly that there is a gametic system characteristic of each species, 

 and two systems when combined in crossing are not able to form permanent 

 combinations, but separate at once in Fo, and this regardless of the visible 

 differentiation. For proof of this, the uniform experience with the fixed hetero- 

 zygous races, which were in appearance alike and uniform, were shown by 

 accurate measurement to be not like, but different, and to produce groups whose 



