74 WILLOW-LARK. 



last state. The water- eft is continually climbing 

 over the brims of the vessel, within which we keep 

 it in water, and wandering away ; and people every 

 summer see numbers crawling out of the pools where 

 they are hatched, up the dry banks. There are 

 varieties of them differing in colour ; and some have 

 fins up their tail and back, and some have not.* 



LETTER XIX. 



TO THE SAME. 



SELBORNE, August 17, 1768. 

 DEAR SIR, 



I HAVE now, past dispute, made out three dis- 

 tinct species of the willow-wrens, (motacillte trochili,) 

 which constantly and invariably use distinct notes. 

 But, at the same time, I am obliged to confess that 

 I know nothing of your willow-lark, f In my letter 

 of April the 18th, I had told you peremptorily that 

 I knew your willow-lark, but had not seen it then ; 

 but, when I came to procure it, it proved, in all 

 respects, a very motacilla trochilus ; only that it is 

 a size larger than the two other, and the yellow- 

 green of the whole upper part of the body is more 

 vivid, and the belly of a clearer white. I have 

 specimens of the three sorts now lying before me ; 

 and can discern that there are three gradations of 

 sizes, and that the least has black legs, and the other 

 two flesh-coloured ones. The yellowest bird is con- 



* The fins, or membrane on the tail and back, increase greatly 

 at the season of generation ; at other times they are hardly per- 

 ceptible. W. J. 



f Brit. Zool. edit. 1776, octavo, p. 381. 



