152 EVENINGS AT THE MICROSCOPE. 



The broad portion of the object before us, forming its 

 bottom part bristling with coarse black hair, is the front 

 of the head of a Blow-fly. From the midst of this projects 

 a dark brown mass terminating in two points, and in- 

 closing a narrower and darker object with two long slender 

 roots, dilated at their bases ; this is the pair of maxillae 

 altered and modified into a kind of sheath for the man- 

 dibles. On each side projects an elegant club, bristled 

 with coarse black hair, and covered besides with a coat 

 of very minute hairs ; these clubs are the maxillary 

 palpi. 



But now we come to the terminal part, consisting of a 

 pair of lobes, together forming a rounded triangle in their 

 outline. This is the dilated and thickened termination of 

 the labium, and is the instrument by which the liquids are 

 so rapidly sucked up. It is impossible to describe this 

 beautiful structure intelligibly ; and, indeed, it is not well 

 understood even by those who have devoted their lives 

 to this branch of natural science. The principal feature 

 apparent is a wide clear membrane, through which runs 

 with admirable symmetry a series of tubes. These tubes 

 consist of four primary ones, all originating near the 

 centre of the expansion, and radiating thence, two back- 

 ward towards the two lateral angles of the triangle, and 

 the other two nearly side by side towards its point. 

 From each of these, along its outer side only, branch off 

 the minor tubes, very numerous and close together, going 

 off in a slightly sinuous line direct to the margin, diminish- 

 ing regularly in their course, and at their extremities 

 curving over, so as to bring their open tips to the surface 

 of the skin. 



The construction of these tubes is highly interesting : 

 they are formed, like the air-pipes {trachea), of a multitude 

 of horny rings ; but with this peculiarity, that the rings 

 do not form a continuous spiral, but are separate and 

 distinct, and are moreover imperfect ; for each wire (so to 



