E. Hindlb and Gr. Meeriman 
211 
a window so that the ticks walked in a definite direction away from the 
light. A crescentic barrier of the substance to be tried was arranged 
across the filter paper in such a position that in walking away from the 
light the ticks were bound to come in contact with it. The following 
results were obtained 
(a) Experiments with liquidsb 
(i) Water. 50 second stage nymphs were employed. On 
reaching the barrier all hesitated, but finally 46 crossed whilst 4 skirted 
round the moist area. 
(ii) Ammonia. The same ticks were employed for this experi¬ 
ment. In this case the ticks stopped before reaching the barrier, but 
after some hesitation 4-5 crossed whilst 5 skirted the barrier. It should 
be added that by the time the ticks crossed the liquid the smell of 
ammonia was very faint. 
(iii) Phenol. The results obtained in this case were precisely 
similar to those obtained with ammonia. 
(iv) Glacial Acetic Acid. Reaction similar to the preceding. 
(v) Clove Oil. 50 second stage nymphs were employed. All 
showed a well-marked reaction to the smell. Before reaching the 
barrier all the ticks retreated, 17 skirting completely round the liquid. 
Finally, however, 33 crossed the barrier but with obvious distaste. 
(vi) Olive Oil. 50 second stage nymphs were employed. In 
this case the ticks did not retreat until after they had actually marched 
into the oil. Eventually 36 crossed the barrier, whilst 14 went back 
and skirted it. 
(b) Experiments with solids. 
(i) Sand. 50 second stage nymphs were employed. All except 
3 ticks walked directly across the sand without any hesitation. 
(ii) Naphthalene. The same ticks were again employed. In 
this case all except 3 crossed the barrier but exhibited slight hesitation 
before coming in contact with it. 
(iii) Ammonium Carbonate and Keating’s Powder respectively, 
gave similar results to naphthalene. 
In all the previous experiments it was possible that the ticks had 
been unable to display their full reactions to the various odours owing 
to the preponderating influence of their negative phototropism tending 
1 In all these experiments the filter paper was merely moistened with the liquid. 
14—2 
