J 64 Bulletin Wisconsin National History Society. [Vol. 9, No. 4. 



dom is so contradictory and shows such variation and adaptabil- 

 ity that the more reasonable explanation in this case seems 

 merely to be that the series of experiments were incomplete, as 

 the authors themselves intimate. In other words, the expected 

 would be that in the next generation, or the one following (or 

 even in tenth) the sex of the progeny would be reversed and be- 

 fore very long the American series would become the lyotokous 

 and the Austrian arrhenotokous and both on occasion amphotero- 

 tokous. Even in the few observed cases, in the Austrian series, 

 traces of a break occur fulfilling expectations (thus once both 

 sexes were produced and thrice males). The determination of 

 sex remains as yet so unsatisfactorily explained and parthenogen- 

 etic reproduction occurs under so many different phases that it is, 

 I believe, uncalled for at present to separate races or species 

 according to whether one is (for all we know to the 

 contrary, temporarily) arrhenotokous and the other the lyoto- 

 kous or amphoterotokous as the case may be. If so, we must ex- 

 pect complete confusion of the two within the course of events, 

 maybe after several months only or it may be not until after sev- 

 eral years. The locality in this case is of course coincidental only. 

 We know that parthenogenesis in a species is very irregular ; 

 males only may be produced generation after generation, then 

 suddenly the sex reversed and so on. This is no reason, there- 

 fore, for distinguishing races or species for purposes of systematic 

 zoology, at any rate certainly not species. It would be very 

 much like separating species because a certain chance series of 

 individuals were favorable to one food while others were favor- 

 able to another, mere cases of individual "choice" or adaption. 

 That morphologically similar bacteria are called species because 

 of their different reactions to definite media is true but that is 

 evidently for convenience, begs the point at issue and confesses 

 probable ignorance. They are not distinct species from any stand- 

 point, systematic or otherwise. If Tachina mella and T. lavarum 

 are morphologically alike, then they are one species and should 



