20 COMPARATIVE ANATOMY. 



Succeeding the maxillae is a pair of jointed appendage*, 

 armed with a small claw. The next are the large cheliform 

 poison -fangs. These are armed with claws, and the extremity 

 of each claw is perforated by the aperture of a small duct lead- 

 ing from a poison-gland. The basal joints are confluent, so 

 that by this union a second labium is formed posterior to the 

 first. The two last-mentioned appendages may be taken as cor- 

 responding to two of the three pairs of maxillipeds in the 

 Lobster, and to the two anterior pairs of legs in Insects. 



The segment to which the large 'chelae' are attached is 

 larger than the segment immediately succeeding it. 



30. A Centipede (Scolopendra), dissected to shew the 

 digestive and female generative systems. 



The animal has been laid open along its dorsal surface, so as 

 to expose the alimentary canal, which is simple, and passes in 

 almost a straight course from mouth to anus, the terminal por- 

 tion of the intestine alone indicating any approach to a con- 

 volution. It is distended with food. The stomach, which 

 occupies the central third of the body, is the widest part of 

 the canal : it communicates anteriorly with the mouth by a 

 narrow oesophagus, and posteriorly is marked off from the intes- 

 tine by a slight constriction. The intestine, at its j unction with 

 the stomach, though of less calibre than the latter, is yet of 

 considerable size; but diminishes as it proceeds, and after de- 

 scribing a sigmoid flexure terminates in an anus. 



The ovary is a long and simple tube, attached above to 

 about the middle of the stomach, and gradually diminishing 

 in size till it reaches its vaginal outlet. The ovi-sacs may be 

 seen through its semi-transparent wall throughout its whole 

 extent. 



The white caeca pinned on either side of the lower part of 

 the preparation are the ' accessory glands.' 



31. A Centipede (Scolopendra), dissected to shew the male 

 generative organs. 



The animal has been laid open along its dorsal surface, and 

 the digestive tract removed. The testes consist of a series of 

 pairs of fusiform vesicles, each vesicle being applied along its 

 whole length to its fellow, from which however it can be easily 

 separated. They occupy a considerable portion of the abdomen, 



