THE BIOLOGICAL EVIDENCE 85 



defects are innate that the defects would not develop equally in 

 country children were they transferred early in life to the slums. 1 

 At present the reader may be inclined to regard these criticisms as 

 frivolous and overstrained, but he will find later there is ample 

 warrant for them. 



136. Much the same objections may be taken to Professor 

 Ewart's inferences. Evidently his birds acquired the disease in 

 their native habitat, and, since so many or all of them had the 

 malady, it is doubtless very prevalent there. Evidently, again, 

 since the disease resembles malaria, since it travelled from India 

 in the birds, and since so many birds were suffering from it, it is 

 a malady of long duration. If, then, it is a cause of sterility, we 

 are left to wonder how, under the conditions, the race has persisted 

 in India. But granting that it is a cause of sterility, it does not 

 follow that it is a cause of variations. As a fact Ewart's experi- 

 ments prove only that, like other cells, the germs, and even the 

 germ-plasm may be enfeebled by toxins ; they do not prove 

 that the hereditary tendencies are thereby altered. His deduction 

 might have been, but was not, tested by showing that the so- 

 called variations were transmissible to descendants. Ewart himself 

 supplies clear evidence that the germ-plasm was not altered, for 

 one of his Indian birds, which, when diseased, had offspring 

 resembling the English parent, after recovery had offspring 

 resembling itself. Evidently the germ-plasm that remained in 

 this bird was capable of recovering from its enfeeblement, and 

 we have no reason to suppose that the germ-plasm which passed 

 from him and entered a healthy female body was less capable of 

 recovery. It certainly fertilized the ovum, and the fact that the 

 offspring resembled the English parent is no proof that succeeding 

 generations would not have reproduced the Indian characters. 

 Professor Ewart has, indeed, furnished warrant for believing that 

 the condition of the germ-plasm at the time of conjugation deter- 

 mines to some extent the characters of the offspring, but no warrant 

 for supposing it fixes the characters of subsequent descendants. 

 All that is demonstrated is that enfeeblement of germ-plasm may 

 render latent for a generation the characters of the parent whence 

 it is derived. The force of this objection is even better seen in 

 the experiments by which he influenced the characters of rabbits. 

 In fact, his observations seem rather to elucidate the conditions 

 under which latency occurs than the conditions under which 

 variations arise. It has long been known that sexual characters 



1 See 732-5. 



