454 



COMPARATIVE ANATOMY 



CHAP. 



pointed process answers to the coxal spur of Scolopendrella. The coxal saccules 

 and spurs of Campodea must therefore be regarded as remains of coxal joints of 

 abdominal limbs, in short, as rudiments of coxse. Similar organs are also found in 

 other Aptera (Figs. 314 and 315), principally in the Thysanura. On the other hand, 

 the coxal rudiments may be wanting or be limited sometimes to the saccules and 

 sometimes to the spurs. It is interesting also to relate that the above-mentioned 



L V- 



FIG. 315. A ventral shield of Machilis maritima, 

 with two protrusible saccules (cb) on each side. On 

 the left the saccules are withdrawn, on the right pro- 

 truded, hs, movable appendages (coxal spurs), muscles 

 of the same and of the protrusible saccules (after 

 Oudemans). 



ft- 



FIG. 314. Ventral side of the hind-body of a female Machilis maritima (after Oudemans). 

 The left half of the 8th ventral shield is removed. I-IX, segments of the abdomen ; c, bristle-like 

 jointed appendages (cerci) of the 10th abdominal segment ; cb, protrusible saccules = coxal glands in 

 the act of degenerating ; hs, movable appendages=coxal spurs, conjectural rudiments of abdominal 

 feet ; Ir, ovipositors. 



processes on the abdominal segments of the Thysanura were by many observers at 

 once assumed to be degenerated abdominal feet. 



In the winged Hexapoda (Pterygota) rudiments of abdominal feet have also been 

 observed. They appear at certain embryonic stages exactly like the rudiments of 

 the thoracic feet, i.e. as prominences or stumps on the most anterior, or on several 

 anterior, or on all the abdominal segments, sooner or later again to disappear. They have 

 been observed in Coleoptera (Hydrophilus, Fig. 316, A and JB, Melolontha), Orthoptera 

 (Gryllotalpa, Mantis, Periplaneta, (Ecanthus, JBlatta), and Trichoptera (Neophalax 

 concinnus}. In a few forms (Gryllotalpa, (Ecanthus, Periplaneta, Blatta, Melolontha) 

 the rudiments of the 1st pair of abdominal feet, before the hatching of the embryo, 



