Pkoblems of Gametic Constitution 81 



the individual that cross over from one to the other of the two parental gametic 

 systems, while the major proportion of the features of each parent retain their 

 integrity and come out in gametogenesis, either pure or with interchanged 

 characteristics. 



This regular interchange of characteristics, the typical Mendelian reaction, 

 is now so well established in many plants and animals from the observations of 

 so many independent observers that there is no question but that it represents a 

 general type of activity in the reactions of the germ-plasm in all living forms. 

 It, moreover, is the mechanism whereby much heterogeneity is produced in any 

 population of organisms. 



The essential problem is, however, what is the cause of the interchange of the 

 gametic factors, and why is it so regularly between equivalent productive centers 

 of action in the germinal material ? In my materials, why does L. signaticollis 

 show no interchange of characteristics when crossed with L. diversa, and inter- 

 changes when combined with L. undecimlineata? In the first combination the 

 entire gametic mass acts as a unit, and in all cases retains its integrity and 

 identity through all operations, in all its qualities and attributes, while in the 

 second there is interchange of larval pattern and larval body-color, each as 

 independent units, as the regular behavior, and, under certain conditions of 

 combinations, also show interchange of characteristics of the antennae, pronotal 

 pattern, sculpture and so on. 



That the observed conditions are due to any chromosome behavior, at least 

 any that is now known, seems to me highly improbable. That the interchange 

 is due to difference in gradient or in potentiality there is no evidence. More- 

 over, if it is some sort of chromosome reaction, produced by the breaking of the 

 rods in synopsis or at some other time in gametogenesis, what is the mechanism 

 that produces the regular random interchange and the mathematically regular 

 classes of gametes ? 



It seems to me, from the many instances that have passed through my hands, 

 that the operation is not that of any morphological action, but of some chemical 

 transposition of materials between the two gametic masses and to be a reaction 

 rather typical of ordinary metathesis of the type common in chemical com- 

 binations, i. e., 2HCl-|-CaC02 = CaCl2 + H2C03. In other words, the gametic 

 materials of one parent, in certain combinations, through some purely chemical 

 affinity, have stronger attraction for the position held by an equivalent com- 

 ponent than for the original position, pass over to the new, displace the second, 

 and occupy its position, while the second passes back to the position occupied by 

 the first. Or it may be that the conditions in the united gametic masses, before 

 their final separation, set free all of the agents of this one sign which are then 

 free in the germinal material, and later attain to a purely chance distribution in 

 the gametic compositions, giving essentially equal numbers of the different com- 

 binations of the two gametic bases and the transposed or one-time dissociated 

 agents. 



However it is attempted to symbolize the nature of this reaction, the fact of 

 there being some reaction that is productive of the differences in perceptual 

 experience with the different somas produced is beyond doubt. The most logical 

 interpretation of the gametic portion of the phenomena, upon the basis of known 

 chemical or physical bases, is that there has been actual passage of centers of 



