190 



Some further remarks upon the Fly's Probosois, 

 By B. T. LowNE, M.R.C.S. Eng., &c. 



(Read April 23rd, 1869). 



The necessity for making some further remarks upon the Pro- 

 boscis of the Blow-Fly occurred to me for two reasons : first, because 

 I described certain structures in my former paper under names, and 

 attributed functions to them, which were the result of too slight an 

 investigation of this difficult piece of anatomy ; and secondly, 

 because I have discovered several most important structures since I 

 made that communication. 



The fulcrum, described in my former paper, is a far more im- 

 portant organ than appeared at first sight, being in point of fact 

 the sucking pump of the proboscis : its walls are double, and these 

 are kept in close apposition by their elasticity, but are capable of 

 being drawn asunder by the action of the muscles which fill the 

 hollow of the organ, opening a cavity between them which is con- 

 tinuous above with the oesophagus, and below with the mouth of 

 the insect. The opening of this cavity draws the fluid from the 

 mouth and sucker of the proboscis, and its closure, which is effected 

 by its own, elasticity, forces the fluid with which it becomes filled 

 into the oesophagus and stomach. The necessity for valves is 

 obviated by the peculiar manner in which the muscles of this organ 

 act, the lower fibres contracting and relaxing before the upper 

 ones, so that a wave-like motion is given to the anterior wall of the 

 cavity. 



The terminal joint of the proboscis encloses the ligula— a thin 

 pointed chitinous piece, extremely delicate at its free extremity, and 

 covered with fine seta3 ; the upper portion of this piece is united 

 closely with the labium, and the salivary duct opens upon its 

 anterior surface. The epiglottis, with its lateral appendages, has 

 already been described by me as being tubular above, and enclosing 

 the oesophagus ; but if that tube be considered to cease at the 

 superior extremity of the fulcrum, where its walls become corneous, 

 some modification of these terms will be advisable ; the fulcrum 

 may be considered analogous to the pharynx, and either term ap- 

 pears to me equally applicable ; the epiglottis, which is really a 



