HARDWICKE'S SCIENCE-GOSSIP. 



253 



The dentition of this creature may be expressed in 

 the following formula, viz. 1,1,2,3,3,4,4,4,3,3,2,1,1,1 ; 

 the two single laterals occupy the posterior portion of 

 the mouth, the three single ones the anterior. It 

 will be seen there are fourteen of these organs in the 

 primary set, in the second set there are nine, in the 

 third set the number is reduced to seven, and in the 

 fourth they are still further reduced to three. Each 

 lobe of the labium is furnished with a group of 

 thirty-three teeth. The laterals are small, and 

 appear to spring from the main trunk of the pseudo- 

 trachea?, a peculiarity not observed in any other 

 specie's so distinctly as this, though it may occur, as 



devoid of the curve, and taper gradually to the 

 apex. 



The succeeding rows are of a uniform type, pre- 

 senting a somewhat similar appearance to the blow- 

 fly ; but they are much more deeply cleft, and instead 

 of being V-shaped, they are more U-like in form. 

 The primary set are of a bright amber tint, but the 

 whole of the succeeding rows are very pale and 

 delicate in appearance. This condition may be 

 permanent, but there is reason for thinking it may 

 be affected very considerably by the period which 

 has elapsed between the emergence of the fly from 

 the pupa-case and its capture. It is well known that 



SCALE OF lOOOti 1 OF AN INCH. 



Fig. 163. — Two of the pseudo-trachea of Musca mcridiana, showing the supporting membranes a a'. 



even in the present case the employment of a rather 

 high power is necessary to bring them into view. 

 Considering the size of the entire group, the various 

 rows are not so distinctly separated as in many other 

 species. For this reason very careful adjustment is 

 absolutely necessary in order to display them. 



The primary row consists of rather broad, stout 

 teeth, terminating in lancet-shaped points. The 

 peculiarity, however, is the sudden curve which is 

 made towards the free end of the organ ; this is 

 peculiar to all the teeth of the primary set, with the 

 exception of the laterals which in* the formula are 

 represented by the single figures ; these are quite 



chitine in its early stages is colourless, or nearly so, 

 and that by the action of the air — and very probably 

 light also — the darker shades are attained, and its 

 permanent hardness established. Specimens of this 

 fly have been dissected in which it was extremely 

 difficult to detect the fourth row of teeth by any 

 change of tint, the most delicate manipulation of 

 light was necessary to discover the outline of the 

 membrane, which would have undoubtedly developed 

 into organs more easily seen, had the creature's career 

 not come to such an untimely end. 



The illustration accompanying these notes is a 

 departure from the course hitherto pursued. A 



