BY W. R. COLLEDGE. 73 



pleasure, and then move slowly up and down until the work is 

 finished. 



Froui a lateral view, the bulb appears to be oval, and 

 presumably like an egg, and I was much surprised one day on 

 turning it on end to find from that point it resembled the letter 

 Y. Fig. 16 shows how it appears in that position. The lower 

 portion is composed of two concave plates set together with 

 their concave surfaces directed outwards. Then a V shaped 

 piece let into the top, completes the organ. Thus all the inner 

 surfaces are in close touch everywhere, and no residual liquid 

 can be found in the pump when at rest. On the aesophagial 

 end there are a number of coarse branching fibres as in fig. 17. 

 But what their function is I do not know ; they are too 

 numerous to be mere points of attachment for the gullet. 



The Poison Glands. 



are seen in fig. 18. Three glands united at one end form a set. 

 And there are two pairs, one on the left, tht other on the right 

 side of the chest. They are long in the Scots Gray, curl, and 

 have a tendency to enlarge at their free ends. A good idea of 

 their size is gained by fig. 19. This is a single gland from one 

 of the sets. To prevent it from being crushed on the microscope 

 by the cover glass, I placed two little pieces of hair from my 

 head on each side, on lowering the glass the gland swung round 

 until it touched one of the hairs, which now projects across the 

 picture, the gland apparently hanging from it. It is thus seen 

 to be about the thickness of a human hair. Those belonging 

 to smaller mosquitoes are still less in size. Right through the 

 centre of each gland runs a fine tubule, and attached to it at 

 right angles are a series of long oval cells ; they are arranged 

 like the hairs on a bottle brush, the tube taking the place of 

 the wire. In these cells the salivary and poison fluids are 

 secreted, and discharged it) to the central tubule. Thence after 

 coalescing with the tubules of the other two glands of its set, it 

 passes up to the neck where it unites with the tube of the 

 opposite set, it continues along the neck and under part of the 

 head until it reaches the base of the proboscis, and there it dips 

 into the centre of a little cup on the base of one of the lancets. 

 It is not the large central one through which the blood is 

 pumped. If it were so, then the incoming current of blood 

 would divert it into its own stomach. But it unites with one of 



