340 Mr. Lubbock on the 



fio-. 7, d. On the posterior segment, and close behind the last of 

 tlie three lateral spines, is the large spiracle, which is situated on 

 a short projection. Behind this, again, on the posterior margin of 

 the body is a long seta, at the base of which and on the median side is 

 a short process terminating in a spine like those on the side of the 

 body. The seta is about -g^th of an inch in length. The second 

 and third (mesothoracic ?) segments differ from the posterior ones 

 in not having any border along the posterior margin, while the 

 second segment offers the additional peculiarity of having a border 

 along the front. 



The second segment, which is received into and as it were fills 

 up a recess in the mesothorax when the head is retracted, gives 

 the body a regularly oval form, though somewhat, as it were, cut 

 off at the posterior extremity. It bears also on each side of the 

 middle line a seta about as large as that at the posterior extremity, 

 and at its posterior angles are also two spines, the anterior of 

 which is a^o^o*^^^^ °^ ^'"^ >"ch, — the posterior, though broader, only 

 ^_3_^ths of an inch, — in length. The head, when extended, ter- 

 minates in a transverse spindle-shaped body, having two lateral 

 tapering lobes, which are slightly curved at their extremity, and 

 are clothed with delicate bristle-like papillae. On each side of 

 the basal portion open the anterior spiracles, and in front of them, 

 but rather towards the middle line, is on each side a seta (PI. XL 

 fig. 1), about 3^^th of an inch in length. This seta is generally 

 directed forwards, while the four long thoracic and abdominal 

 setae are often directed perpendicularly upwards. In front of the 

 long spine on the anterior part is a short unjointed appendage 

 (PI. XL fig. 4), and in front of this again and still nearer the 

 middle line is another still shorter (PI. XL fig. 3). 



The upper margins, as already mentioned, project like wings 

 beyond the softer parts of the body. Seen from below, these parts 

 offer indistinct segmental divisions, and each seginent has a 

 lateral papilla, which probably fidfils the functions of a foot. At 

 the posterior margin of the fleshy parts are eight papillae (PI. XL 

 fig. 8, a), some of which, however, are not very conspicuous. 

 Beneath this posterior margin lie two large lobes, shaped some- 

 what like a short human foot (PI. XL. fig. 8, b), attached as it 

 were by the ankle. 



Both the upper and under walls of the body are so transparent 

 that many of the internal organs can be seen through them. The 

 upper surface of the fourth segment (exclusive of the head) has on 

 each side near the front border and almost over the tracheal tube, 

 a smiill round orifice (PI. XL fig. 1, g). 



