( vii ) 



which filled the box, it is possible that their egg-laying in- 

 stincts had been dulled during captivity under these con- 

 ditions. The eggs laid were separated into four lots : P. 

 humanus laid on hair, P. liumanus laid on flannel, P. capitis 

 laid on hair, and P. capitis laid on flannel. Individuals were 

 reared from these eggs, and 12 (J c? and 12 $ $ of each lot 

 were placed in boxes containing human hairs and lined with 

 flannel, similarly to those used in the former experiment. 

 After five days, during which all four batches were fed and 

 exposed to the same conditions, the eggs were counted and 

 their positions recorded as follows : — 



P. humanus, bred from eggs laid on hairs : — 



no J 10 r on hairs 38 = 11% 



12 and 12 , , , 



on gauze cover 01 box ... 1 



^ 1 on flannel, side next box . . 37 = 10% 



^^^^- [ on flannel, exposed side . . 283 = 79% 



The eggs were laid on hairs only where these came in contact 

 with flannel. 



P. humanus, bred from eggs laid on flannel :— 



12 and 12 { on gauze cover of box . 

 produce 344 - on flannel, side next box 

 eggs. I on flannel, exposed side 



P. capitis, bred from eggs laid on hairs : — 



12 and 12 f on gauze cover of box . 



produce 274 - on flannel, exposed side only 



eggs. I on hairs 259 = 95% 



P. capitis, bred from eggs laid on flannel : — 



on gauze cover of box , . . 4 == 1% 



on flannel, exposed side only . 2 = |% 



on hairs close to flannel . . 2 = 1% 



on hairs 382 = 98% 



12 and 12 

 produce 3 CO 

 eggs. 



Although this result leaves the question of specific identity 

 still undetermined, it suggests that there is a clear line of 

 demarcation as regards the egg-laying instinct, provided the 

 insects are left an element of choice. 



