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the lateral portions of tlie fulcrum and support above the maxillary palpi; the 

 labium, as submentum, mentum, etc., extends anteriorly from the base of the 

 fulcrum and terminates in the labellae. Gerstfeldt's views of the homologies of 

 the different parts of the fulcrum seem utterly untenable, as will appear later. 



LowNE, 23 in 1870 (p. 41-51, pi. 2-3), describes and figures the proboscis and 

 its parts in Musca vomitoria. He describes fully, and in general accurately, the 

 fulcrum, which he regards to be homologous with the fulcrum of bees. The 

 labrum-epipharyux, Lowne thinks, is composed of the labrum united with the term- 

 inal lobes of the maxillae, and he terms the organ as a whole the operculum, 

 because it shuts like a lid over the other mouth-parts. Lowne correctly describes 

 the hypopharynx under the name of tongue. The labium, which he calls the 

 canula, is considered to be the united labium and mentum. I do not here go 

 into further details in regard to Lowne's work, because I shall have occasion to 

 notice it often in the following pages. 



MACLOSKIE, in 1880, describes the proboscis of the house-fly, Musca domestica, 

 using for the most part 'Lowne's terminology, and discusses briefly several points 

 about its homologies and functions. Among other things he again affirms the 

 statement that inflation plays a prominent part in the extension of the proboscis, 

 a statement criticized by Suffolk, 21 in 1869. Macloskie writes (p. 157-158), 

 "It is easy to dispose of Mr. Suffolk's hasty criticism. Immerse the head of the 

 fly in caustic potash, which destroys the muscles, the chitine of the membranous 

 sheath and the tracheal tubes remaining intact, and you can still protrude the 

 organ by slight pressure. Further, when the proboscis is pressed out and all its 

 parts distended, pierce with a needle the swollen air sacs under the tip, and at 

 'once the tip collapses upon the mentum. If you tear the membrane about the 

 base of the proboscis that part collapses. If you press the head over much, the 

 membrane-sheath sends out bulging processes which soon burst, sending bubbles 

 of air through the water in which you are examining it." I have verified the 

 experiments mentioned by Macloskie above, besides trying others, and I think that 

 an important factor in the cause of the extension of the proboscis of Musca is 

 the injection of air into it. Macloskie also homologizes the fulcrum of the diptera 

 with the endocranium of the cockroach (Blotto), a view that I ana not prepared 

 to affirm or to deny; but his conclusion that the so-called middle section is the 

 true base of the proboscis, the so-called basal portion being a part of the head, 

 and its organs internal, rather than true mouth-parts, this latter conclusion I 

 hope to be able to prove in the concluding part of this paper. 



MENZBIEE (p. 62-66) describes the organs which constitute the proboscis of 

 Musca, and which are, according to him, the following: a labrum united to an 



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