194 W. H. FURLONGE ON THE PULEX IRRITANS. 



blades of chitin, the outer surfaces of each being convex, so that, 

 when closed together, they form a tubular channel or sheath, within 

 which the suctorial organ, or ligula, is situated. Around both edges 

 of each curved blade, is set a row of glittering, very transparent, 

 round and pointed teeth, curving backwards or upwards. These 

 teeth are not formed by the serration of the edges of the blade, 

 but appear to be composed of a different and somewhat glassy mate- 

 rial, and are inserted, separately, in the substance of the mandibles — 

 after the same manner in which the teeth are set in the rostrum of 

 the saw fish, to the structure of which, Gosse aptly compares that 

 of the mandibles of the flea. Immediately behind the marginal 

 fringe of teeth, and running parallel with it, along the outer or 

 convex sides of the blades, is placed a second row of glassy teeth, 

 which seem to me to possess a totally different structure from those 

 of the margin, being shorter and stouter, somewhat pyramidal in 

 shape, and standing perpendicularly upon square bases ; and they, 

 moreover, do not appear to be inserted in sockets as in the case of 

 the marginal teeth. Each row contains about 75 teeth, so that the 

 four double rows upon the pair of mandibles are furnished with no 

 fewer than about 600 separate teeth ! 



The Ligula or Suctorial Organ, as just stated, lies between the con- 

 cave surfaces of the mandibles, which, when brought together, 

 surround and protect it. It consists of an elongated, slender, flexible, 

 proboscis, having, as I believe, an annular muscular structure, at 

 least, the tubular channel running through it is certainly striated. 

 The ligula originates at its junction with the alimentary canal, in 

 an elongated fusiform cavity, and terminates in a somewhat bulbous 

 enlargement, the orifice of which is distinctly fimbriated, though 

 this structure can only be made out by the employment of an objec- 

 tive of very high power, say a one-sixteenth. Along one side of 

 the organ is set a series of 11 or 12 rounded, or sub-angular, pro- 

 jections (see Fig. 5) which are placed at regular and rather wide 

 intervals, for about one-half of the lower portion of the ligula. It 

 is extremely difficult to determine, with accuracy, the true nature 

 of these prominences, but I think I am in a position to state, with 

 tolerable certainty, that they consist of thin rounded plates or teeth 

 of chitin, set edgewise in the substance of the organ, and connected 

 by exquisitely thin cutting edges, curving down between the pro- 

 minences — the whole arrangement very much resembling the saw 

 of some species of saw flies. The use of this curious organ is doubt- 



