234: 



THE MICROSCOPE AND ITS REVELATIONS. 



powerful teeth, opening laterally on either side of the mouth, and serv- 

 ing as the chief instruments of manducation; 2, a second pair of jaws, 

 termed maxillce, smaller and weaker than the preceding, beneath which 

 they are placed, and serving to hold the food, and to convey it to the back 

 of the mouth; 3, an upper lip, or Idbrum; 4, a lower lip or labium; 5, 

 one or two pairs of small jointed appendages termed palpi, attached to 

 the maxillae, and hence called maxillary palpi; 6, a pair of labial palpi. 

 The labium is often composed of several distinct parts; its basal portion 

 being distinguished as the mentum or chin, and its anterior portion being 

 sometimes considerably prolonged forwards, so as to form an organ which 

 is properly designated the liqida, but which is more commonly known as 

 the ' tongue/ though not really entitled to that designation, the real 

 tongue being a soft and Drojecting organ which forms the floor of the 



FIG. 428. 



Tongue of common Fly: a, lobes of ligula; 6, portion inclosing the lancets, formed by the- 

 metamorphosis of the maxillae; c, maxillary palpi: A, portion of one of the pseudotracheae 

 enlarged. 



mouth, and which is only found as a distinct part in a comparatively 

 small number of Insects, as the Cricket. This ligula is extremely devel- 

 oped in the Fly kind, in which it forms the chief part of what is com- 

 monly called the 'proboscis' (Fig. 428) ; J and it also forms the ' tongue' 

 of the Bee and its allies (Fig. 429). The ligula of the common FJy 

 presents a curious modification of the ordinary tracheal structure 



1 The representation given in the figure is taken from one of the ordinary prep- 

 arations of the Fly's proboscis, which is made by slitting it open, flattening it out, 

 and mounting it in Balsam. For representations of the true relative positions of 

 the different parts of this wonderful organ, and for minute descriptions of them, 

 the reader is referred to Mr. Suffolk's Memoir ' On the Proboscis of the Blow-fly/ 

 in " Monthly Microsc. Journ.," Vol. i., p. 331; and to Mr. Lowne's Treatise on 

 " The Anatomy and Physiology of the Blow-fly," p. 41. 



