BY T. HARVEY JOHNSTON AND M. J. BANCROFT. 303 



grown cattle. The object in view wa.^ to ascertain if the 

 resistant qualities enjoyed by the daughter of Clover would 

 be convej'ed to the progeny of a very susceptible subject. 

 Result :— Both calves retained resistance while runn- 

 ing free with ordinary cattle until the summer of 1915, 

 when, owing to drought conditions, they 'necanie poor and 

 emaciated, maturing fully engorged ticks to such an extent 

 that treatment became necessary. Both are still under 

 observation to n.scertain whether, with improved conditions, 

 this resistance will become established. The calf of Brownie 

 (Spot) is still living and will be used to determine whether 

 the resistance enjoyed by its pr.rent (and possibly obtained 

 by contact from Wallura) has })ten transmitted.* 



MI. Isolation of nine calves on ter acres of grass 

 land, heavily infested with ticks, six being the progeny of 

 ordinary tick susceptible cattle and three being the progeny 

 of " proven resistant " stock. 



Result : — Three of the controls succumbed to extremely 

 heavy infestation. Two had to be destroyed subsequently, 

 having failed to recover. One recovered but showed no 

 resistant qualities when disposed of. 



The three resistant stock suffered but light infestation 

 and rapidly developed into clean-coated heifers. 



Two of these are identical with the mature cows 

 Donkey and Yellow now registered as resistant, have passed 

 their first period of lactation, both showing serous exudate 

 on escutcheon. 



(Signed) Mijnro Hull, 



February I9th, 1916. 



Fertility of Ticks taken from Resistant Cattle. 



A number of ticks taken from twenty of Mr. Hull's 

 resistant animals during the past three years (1915-1918) 

 have been watched by us in order to determine whether their 

 fertility has become diminished. Ticks from ordinary 

 controls have also been tested. For a considerable time Mr. 

 Hull was not able to raise larvae from such ticks, while 



*Wallum has fully regained resistance and is to-day quite tick-free 

 while Brownie has been carrying a few ticks all throughout the period. 

 10th July, 1916. M. Hull. 



