44 



SOME ASPECTS OF MORPHOLOGY 



the coxites of the ninth segment bear two pairs. The anterior 

 and posterior valves are outgrowths of the medio-lateral margins 

 of their respective coxites and are regarded as secondarily 

 developed formations known as the gonapophyses. The lateral 

 pair of valves borne by the ninth segment on the other hand 

 represent the greatly drawn out coxites and are therefore the 

 modified bases of an original pair of abdominal appendages. The 

 styli, however, are very rarely retained : they are present, for 



Vlll IX 



Fig. 26. Diagram illustrating structure of abdomen and morphology 

 of the ovipositor, c, cercus ; e, epiproct; g, g^, first and 

 second gonapophyses ; /, limb base (coxite) ; la, lamina supra- 

 analis ; la^, lamina subanalis ; p, paraproct ; s, sternum ; 

 sp, spiracle ; st, stylus ; t, tergum ; vii-xi, seventh to eleventh 

 terga. (From Snodgrass, 1931.) 



example, in the rudimentary ovipositor of Mastotermes (Fig. 27) 

 and in the more highly developed organs of some of the Odonata. 

 It is well known that in Machilis the anterior and posterior 

 valves develop alike in connection with their respective segments 

 and form the ovipositor. The lateral valves are undeveloped as 

 such and remain as unmodified coxites, bearing long styli. While 

 the homologies of these lateral valves have been believed to 

 remain constant in different orders, observations by Nel (1929), 

 on the development of the ovipositor in Locustana, Colemania 

 and Blatella, appear to indicate that the anterior valves are 

 modified coxites like the lateral pair, and are consequently not 



