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 pro- 

 jects a dark brown mass terminating in two points, and 

 inclosing a narrower and darker object with two long 

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

 maxillce, altered and modified into a kind of sheath for 

 the mandibles. 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 backward 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, diminishing 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 (trachece), 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 



