538 



JOHN B. SMITH. 



Fig. 22. Mouth parts of 

 Musca dowestica. 



Finally, I will add a figure of Musca dornestica, the common house- 

 fly, in which the parts are named in accordance with what I believe 

 to be their true character. The figure is 

 correct, save in the pseudo-tracheal system 

 of the galea in which no attempt at accuracy 

 was made. 



I have now covered a series, showing, as I 

 believe, the homology between the mouth 

 parts of the Diptera, and the typically man- 

 dibulate mouth. Many more specimens were 

 examined than are here referred to, only 

 those useful to my purpose being selected to 

 figure, and only such characters being se- 

 lected for study as bore upon the present 

 inquiry. I have shown the presence of the 

 true mandibles in Simulivm, and their ab- 

 sence elsewhere. I have traced the " mandi- 

 bles" of previous authors — from a stout, 

 piercing organ, to the "great tendon" — and 

 have shown it to be a palpifer first, aud an attachment for muscles 

 flexing the proboscis finally. As a mere palpifer it may yet, in its 

 development, represent as well the stipes, which I do not otherwise 

 identify. I have proved the " labium" a mandibulate organ, and a 

 modification of the galea. I have shown its original paired character, 

 and its development to the typical muscid proboscis. I have proved 

 its jointed nature, and have identified the chitinous supports of the 

 pseudo-trachea, as the remnants of the original segments. The la- 

 cinia have always been recognized as the " maxillae," and I have 

 sihown to what particular piece they are homologous. I have shown 

 the meutum and the rudimentary labial palpi, and have homologized 

 the labrum-epipharynx and hypopharynx with the ligula and para- 



glossse. 



In ray studies I have followed a different line from that adopted 

 by Dimmock, Macloskie, or Kraepelin. I made no sections of any 

 kind, but studied each organ in its entirety, in its relation to others, 

 and in its development. In other words, my studies were morpho- 

 loo-ical rather than anatomical. 



On mere philosophical and physiological grounds, I claim my 

 interpretation of the parts as the true one. It is perfectly conform- 

 able to any natural theory of evolutionary development ; it accounts 



