154 EVENINGS AT THE MICKOSCOPE. 



lower jaws of the Beetle, being thus greatly developed at 

 the expense of almost all the other parts. The upper lip 

 and the mandibles are discernible only in the form of three 

 most minute plates ; the labial palpi are large and promi- 

 nent, those well-haired points that project in front of the 

 head, one on each side of the spiral. This spiral form of 

 the maxilla is called antlia. 



It is not, however, very easy to fix it in an extended 

 condition on a slip of glass, so as that it shall lie flat 

 throughout its whole length, without injuring the parts 

 or so agglutinating them together that their structure is 

 concealed or distorted, and in either case unfitted for 

 microscopical examination. The specimen which I have 

 prepared, from the mouth of the Small Garden White 

 Butterfly, is stretched, and fixed in balsam, and will, I 

 think, show you the structure under a high power very 

 well. 



Before we examine it, however, I will cite you the 

 description of one of the most eminent of microscopical 

 anatomists, Mr. Newport. He considers each maxilla to 

 be composed of an immense number of short transverse 

 muscular rings, which are convex externally and concave 

 internally, the two connected organs forming a tube. 

 Within each there are one or more large trachea con- 

 nected with the trachea in the head. The inner or con- 

 cave surface which forms the tube is lined with a very 

 smooth membrane, and extends along the anterior margin 

 throughout the whole length of the organ. At its com- 

 mencement at the tip it occupies nearly the whole breadth 

 of the organ, and is smaller than at its termination 

 near the mouth, where the concavity or groove does not 

 occupy more than about one-third of the breadth. In 

 some species, the extremity of each maxilla is furnished 

 along its anterior and lateral margin with a great number 

 of minute papilla. These, in Vanessa Atalanta (the Eed 

 Admiral Butterfly), for instance, form little barrel-shaped 



