Walter Hitciiie 



319 



The second pair of rods (t) lie adjacent to each other on the dorsal 

 surface of the sac and are stouter than the first pair. 



Fig. 17. The median lobe, tegmen, and spiculum gastrale, seen in side view, in their natural 

 position (highly magnified), is = internal sac; ml— median lobe; ms = median strut; 

 sp = spiculum gastrale; < = tegmen. 



The median lobe (ml), roughly speaking, consists of a hollow curved 

 cone of chitin pointed at its apical end. At the basal end, its dorsal 

 surface is split into two parts called the median struts (ms) (Fig. 18 a). 



be d 



Fig. 18. The median lobe, spiculum gastrale, and tegmen showing their various parts 



(highly magnified). 

 Fig. 18 a. Ventral view of the median lobe within the tegmen. 

 Fig. 18 6. Ventral view of spiculum gastrale. 

 Fig. 18 c. Ventral view of tegmen. 



18 d. Median lobe, side view; tegmen removed. 



bp = basal piece; is = internal sac ; 11 = lateral lobes; mf= median foramen ;ml = median 



lobe; mo = median orifice; ms = median strut; t = tegmen. 



21—2 



Fig. 



