GENE'S ORGAN 665 



According to Samson the former stains a brilliant yellow with picric acid 

 and contains delicate threads and many granules. In a tick that is 

 feeding, the middle zone is divided off from the marginal zone and is full 

 of secretory globules ; at the boundary between the two zones there are 

 two or three sausage-shaped nuclei which contain large irregular masses 

 of chromatin. Minute channels conduct the secretion from the middle 

 zone to the marginal, where they join to form a single duct which opens 

 into the main salivary duct on which these glands are situated. 



In the larva the salivary glands are in an immature condition and are 

 unbranched ; as a rule only three or four acini are present. Their number 

 increases in the nymphal stage and the glands become branched. In the 

 adult stage the secreting elements are only fully developed just before 

 and during the act of feeding. In the replete female (Ixodini) the glands 

 soon break up into granular masses and finally disappear when the tick 

 has begun laying her eggs. 



Christophers, and Nuttall and Strickland, have shown that the sali- 

 vary glands of ticks contain a considerable quantity of anticoagulin ; 

 the latter observers found that the anticoagulin present in the salivary 

 glands of Argas persictts may delay coagulation of human blood for 

 forty-five to ninety-five minutes or indefinitely. 



The salivary ducts pass along the sides of the horizontal plate of chitin, 

 and, piercing the mouth ring, open at the sides of the buccal cavity 

 as described above (Plate LXXXIII, fig. 3). 



The coxal gland (Plate LXXXIII, fig. 2) is situated in the anterior 

 third of the body just over coxae II and III and in close proximity to the 



salivarv gland ; it mav be recognized by its white colour 



, , " . . , : . _ " . . . . . The coxal gland 



and by its rich tracheal supply. Each gland is of an 



irregular shape, and consists of one or more lateral lobules. On section 

 the gland and its accessory lobules are seen to consist of a number of 

 gland cells with large irregularly shaped nuclei. The protoplasm of the 

 cells is filled with dense masses of supporting fibrils ; minute excretory 

 channels discharge the excretion from the cells into larger ducts, which 

 open on the coxal joints. The exact function of this gland is unknown, 

 but several observers have noted that a secretion exudes from it, 

 in the case of Ornithodorus savignyi and O. moubata, during the act of 

 feeding ; Christophers states that the fluid is alkaline in reaction and 

 contains an anticoagulin. The gland is present in all female ticks. 



Gene's organ (Plate LXXXIII, fig. 4), also described as the cephalic 

 gland (Christophers) and the sub-scutal gland (Samson), is a large 

 glandular -structure associated with the deposition of eggs, and is 

 84 



