1896.] 267 



from each other, is surely of more importance than that the second 

 brood of crepuscularia had a white ground-colour like the first brood of 

 hiundularia. Most of us have reared a second brood of the " Thorns." 

 All I have seen are smaller and less distinctly marked than the first 

 brood, and I have understood this was a result of the shorter time for 

 development. I have only once had a second brood of biundularia 

 here {crepuscularia does not occur). They were smaller, less distinctly 

 marked, more suffused than the type, and the ground-colour not so 

 white. This confirms Mr. Barrett's experience, for he tells us that 

 the second brood of hiundularia were " actually more tinged with brown 

 than the type." The conclusion that Mr. Barrett arrives at that 

 " the second brood of the brown crepuscularia is obviously hiundularia" 

 should, therefore, be carried one step further, and we should say, the 

 second brood of the white hiundularia is "obviously " crepuscularia. 



We are now in this position. We know that crepuscularia appears 

 in the south in March and April, is brownish, and produces a second 

 brood much whiter than the parents ; that biundularia occurs generally 

 throughout the country in May and June, is whiter, and when a second 

 brood appears, it is more obscurely marked and browner than the early 

 brood. Surely all these different characteristics point to two species, 

 not one. 



Hartlepool ; October, 1896. 



[My friend Mr. Robson's statement of the case is very fair and reasonable ; but 

 he is under more than one disadvantage : he has not seen the specimens ; moreover, 

 he has quoted my remarks I think from memory. I did not write that the second 

 brood of T. hiundularia were "actually more tinged with brown than the type,^' but 

 " than the others," the second brood of crepuscularia of which I had been writing. 

 As a fact the colouring is curiously crossed ; in Mrs. Bazett's second brood of the 

 early brown form it is greyish-vi\\\tei without a tinge of brown, but in the second 

 brood of the white later form there is a tinge of brown and no grey. To my own 

 judgment this indicates identity, and not distinctness of species. Mr. Robson 

 labours under another disadvantage, in which he is not alone, of not having seen the 

 German and Hungarian specimens "selected" and others which I was able to exhibit 

 the other evening at the South London Society, and which are extremely curious ; nor 

 the enormous series (two drawers and a half exhibited by Mr. Tutt and two drawers 

 by Mr. J. Henderson) in which the arbitrary nature of the separation of the two 

 forms into species seemed to me to be evident. Moreover, he also has himself reared 

 a second brood of T. biundularia (the form found in Durham) in the year, and so 

 further helped to sweep away the idea tliat this form is only single-brooded. 



It so happens that another interesting piece of evidence has just come to hand. 

 Mr. G. O. Day, of Knutsford, has most obligingly forwarded to Mrs. Bazett his own 

 (very different) series of the supposed two species, and has permitted her to send 

 them on to me. Among these are no second brood exaniple-;, ami ni>ne oC 1hl^ 



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