252 
Arf/as per si CHS 
In Argas j^ersicus, however, the secretion only appears after 
engorgement, large droplets of clear colourless fluid being discharged 
within a few seconds or minutes of the withdrawal of the proboscis of 
the tick from the wound. 
The explanation offered by NuttalT is, in all probability, the true 
one, viz. “ that the object of this secretion appears to be to permit the 
tick to concentrate the essential food-constituents of the blood in its 
alimentary canal.” The presence of an anticoagulin in the secretion is 
doubtless explained by the fact that the salivary secretion, which is 
ingested with the blood, undoubtedly contains such a principle, and any 
excess would remain in solution in the non-nutrient wateiy constituents 
of the blood. 
It is most remarkable that these two tiny glands should be capable 
of excreting such a large quantity of fluid in so short a time. In an 
experiment which was made by W. F. Cooper and one of us (L. E. K.), 
a fasting female, sent from Rhodesia, was allowed to gorge to repletion 
on a fowl. Immediately it detached itself, it was removed to a small 
glass capsule, the weight of which had been accurately determined, and 
the capsule containing the tick was again weighed, the difference between 
the two weighings giving the weight of the gorged tick. After a minute 
or two, the tick was seen to discharge, quite suddenly, a large drop of 
secretion from the coxal glands, and simultaneously underwent au 
apparent diminution in size. After draining as much as possible of the 
adherent fluid from the surface of the tick’s body and finally drying it 
with filter-paper, the tick was again weighed. The original weight of 
the gorged tick was 0‘0385 gm. ; the weight of the tick after the 
extrusion of the coxal gland secretion was 0'02I5 gm. ; the difference 
between these figures represents the weight of the secretion, viz. 
0 0140 gm.—36'6 “/o of the original weight of the tick ! In all the cases 
observed, extrusion of the coxal gland secretion occurred within five 
minutes of the detachment from the host. 
Coxal glands, the function of which is undoubtedly concerned with 
the excretion of nitrogenous waste products, occur in many Arachnida, 
but in all known examples the openings of the excretory ducts are 
situated on the fifth pair of appendages, which correspond to the third 
pair of legs in the tick. The subject is one which requires further 
investigation to clear up the problem. 
1 Nuttall, G. H. F. (vii. 1908), p. 14. 
