W. H. FURLONGE ON THE PULEX IRRITANS. 193 



pear to serve the purpose, chiefly, of external sheaths or protective 

 pieces, to the more delicate organs situated between them. 



The Maxillary Palpi are a pair of four-jointed, tubular organs, 

 springing from the anterior portion of the head, and, in their normal 

 position, project perpendicularly downwards in front of the other 

 trophi of the mouth. Three of the four joints are cylindrical, 

 slender tubes, or lobes, having a nearly similar length and diameter, 

 the terminal lobes being somewhat flattened and spoon-shaped. 

 The lobes composing the maxillary palpi, are all characteristically 

 marked by several transverse bands of chitin, which nearly surround, 

 and doubtless serve to strengthen, the thin, chitinous walls which 

 envelope them. Their exterior surfaces are thinly studded with 

 short, fine setas, which probably serve to convey sensorial impres- 

 sions to the transparent and, I think, fluid contents of the lobes. 

 In the living animal these organs are in continual, active move- 

 ment, being pointed upwards or laterally, independently of each 

 other, and are frequently applied to the surfaces of external objects, 

 as if for the purpose of ascertaining their nature and properties, in 

 a manner apparently much more analagous to the action of the 

 antennae of such insects as the ants and cockroaches (which seem 

 to be employed as tactile organs) than to the functions of the 

 maxillary palpi of insects in general. I am inclined from these 

 observations, to submit the conjecture, in connection with my hypo- 

 thesis as to the special sense of hearing which I suppose to be served 

 by the true antennas, whether the maxillary palpi may not, in the 

 flea, act as supplementary or pseudo antennas, by conveying impres- 

 sions of surrounding objects, which, from the latent position of the 

 real antennas, these organs are unfitted to acquire ? 



The Labial Palpi are organs of very curious construction. They 

 are each composed of four tubular joints, (see Fig. 6) united or fused 

 at their extremities, so as to form one tubular tenon, in which is 

 inserted a narrow, straight, blade of very transparent chitin. The 

 top or back of the blade is rather thick, but gradually thins, 

 like a wedge, to an exceedingly keen cutting edge. . The extremity 

 of the blade is pointed and projects for some little distance beyond 

 the tenon in which it is set. The tenon itself, is strengthened by a 

 layer of thickened brown chitin, and from each of its divisions two 

 setas project forwards, and four somewhat longer hairs spring from 

 the extremity. 



The Mandibles consist of two very long, thin, narrow and straight 



