66 ON CROSSING AS A CAUSE Chap. XV. 



i it might naturally be supposed that it would take several 

 ■ crosses to get rid of the heavy form of the bulldog ; but 

 Hysterics, the gr-gr-granddaughter of a bulldog, showed no 

 trace whatever of this breed in external form. She and all 

 of the same litter, however, were " remarkably deficient in 

 ' ; stoutness, though fast as well as clever." I believe clever 

 refers to skill in turning. Hysterics was put to a son of 

 Bedlamite, " but the result of the fifth cross is not as yet, I 

 " believe, more satisfactory than that of the fourth." On the 

 other hand, with sheep, Fleischmann 13 shows how persistent 

 the effects of a single cross may be : he says " that the original 

 " coarse sheep (of Germany) have 5500 fibres of wool on a 

 " square inch ; grades of the third or fourth Merino cross 

 " produced about 8000, the twentieth cross 27,000, the per- 

 " feet pure Merino blood 40,000 to 48,000." So that common 

 German sheep crossed twenty times successively with Merino 

 did not bj any means acquire wool as fine as that of the pure 

 breed. But in all cases, the rate of absorption will depend 

 largely on the conditions of life being favourable to any 

 particular character ; and we may suspect that there would 

 be a constant tendency to degeneration in the wool of Merinos 

 under the climate of Germany, unless prevented by careful 

 selection; and thus perhaps the foregoing remarkable case 

 may be explained. The rate of absorption must also depend 

 on the amount of distinguishable difference between the two 

 forms which are crossed, and especially, as Gartner insists, on 

 prepotency of transmission in the one form over the other. 

 We have seen in the last chapter that one of two French 

 breeds of sheep yielded up its character, when crossed with 

 Merinos, very much more slowly than the other ; and the 

 common German sheep referred to by Fleischmann may be in 

 this respect analogous. In all cases there will be more or less 

 liability to reversion during many subsequent generations, 

 and it is this fact which has probably led authors to maintain 

 that a score or more of generations are requisite for one race 

 to absorb another. In considering the final result of the 

 commingling of two or more breeds, we must not forget that 



13 As quoted in the * True Principles of Breeding,' by C. H. Macknight 

 and Dr. H. Madden, 136o, p. 11. 



