VI 



ANTENNA TA H7A'< J8 



455 



become short stalked vesicles of considerable size, which may be compared with the 

 protruded coxal sacs of the ThyKnnurit. A respiratory function has without sufficient 

 foundation been ascribed to both these structures. 



Considering the widespread occurrence of rudimentary abdominal feet in the 

 Embryos of winded Insects we are justified in asking the question, whether the 



B 



4-U 



: r - 1 



fi 



- (L 



FIG. 31t3. .4 and 1; Hydrophilus embryos witti the rudiments of extremities (after Heider). 

 In the somewhat older embryo, B, the rudiments of abdominal feet, which disappear later, can be 

 very distinctly seen ; a, anal aperture ; an, antenna ; g, rudiment of the ventral ganglionic chain ; TO, 

 oral aperture, md, Mandible ; mx\, 1st maxillae ; inxn, 2d maxillae (rudiment of the lower lip) ; pi, 

 P2> Ps> thoracic pairs of legs ; p 4 , p 5 , p?, p 9 , rudiments of extremities of the 1st, 2d, 4th, and tlth 

 abdominal segments ; st, stigmata ; vk, procephalon. 



truncated feet (anal feet) of the larra of butterflies and wasps are not rather the 

 remains of real limbs than new formations. 



C. The Wings. 



Wings 



are altogether wanting in the Myriapoda. Among the 

 Ifi'.mpoda the Apterygota, as their name implies, are entirely wingless. 

 Since neither the adult Apterygota nor the embryos at any stage of 

 their development have wings or organs belonging to wings, we are 

 justified in assuming that their ancestors also Avere Avingless, in short 

 that the Avingless state is as much the original condition here as in the 

 Miji-'i'ipnili and Protracheata. This assumption is not without support 

 from other points in their constitution. All other Hexapoda, hoAvever, 

 are typically provided Avith Avings, and originally indeed with 2 pairs, 

 and although Avithin the different orders of the Pterygota the Avings 



