CRUSTACEA, ARACHNIDES, INSECTA. 5 



in the Honiptera mn\ Diptcra, the mandibles and maxilltr are 

 replaced by scaly pieces in the form of setcE, which arc re- 

 ceived in an elongated tubular sheath, that is either cylin- 

 di'ical and articulated, or formed with more or less of an elbow, 

 and terminated by a kind of lips. In this case they constitute 

 a true proboscis. In others that also live by suction, the Xe- 

 pidoptera, the maxillae alone aregreatly elongated and 'united, 

 producing a tubular setiform body,. resembling a long, slen- 

 der, and spiral tongue (or the spirifrompe^ Lat.): the re- 

 maining parts of the mouth are considerably reduced. Some- 

 times again, as in many of the Crustacea, the anterior feet 

 approach the maxillos, assume their form, and exercise part of 

 their functions — the latter are then said to be multiplied. It 

 may even happen that the true maxilhc become so much re- 

 duced, that the maxillary feet supply their place in toto. 

 Whatever be the modifications of these parts, however, they 

 can always be recognized and referred to a general type(l). 



tera, which appears to me to be analogous to tlie ep'ipharynx. The labrum is to it, 

 what the mentum is to the labium. 



(1) It is only by a compiu-ative and gradual study of the mouth of the Crus- 

 tacea, that we can acquire correct and cxdfct ideas rc'specting the various trans- 

 formations of these parts, and the means of establishing-, if not a certain, at 

 least a probable general concordance between these vai'ious org-ans in tlie three 

 classes. The mandibles, maxilla;, and the labium, are in fact, a sort effect appro- 

 priated to the masticatory or buccal functions, hut susceptible of being- so modified 

 as to become org.ans of locomotion. This principle even extends to tlie antcn- 

 n'x, or at least to the two intermediate ones of the Crustacea, ny adopting it, we 

 are enabled to reduce the composition of these organs to one general type, and 

 we shall hereafter see that, in this respect, neither the Arachnides nor Myriapoda 

 present any anomaly. 



