2JO J. K. WODSEDALEK. 



PLATE II. 



FIG. 4. Representation of the entire organ surrounded by hypoderrnis, as it 

 appears in a mounted specimen. Circular bands can be seen, especially at the 

 edges of the organ, owing to the fact that we look at the vertical portion of each 

 deeply colored part. In this view the large light areas appear at the entrances of 

 the tracheal tubes; this is due to the fact that we look through a comparatively 

 thin portion of the chitin in those regions owing to the direct extension of the cavities 

 of the tubes into the organ. The darker areas appear as such because of their 

 thickness; each is a concentric mass around the organ and forms the partition be- 

 tween the cavities. 



FIG. 5. A horizontal section almost directly through the center of the two 

 posterior tubes and a little above the center of the two anterior ones. It is only 

 natural, therefore, that the two posterior tracheae should lead to the solid central 

 mass. The entrances of the two anterior ones are not in the same plane with that 

 of the posterior pair and therefore the innermost portion of their cavities are not 

 represented in this section. The gradually increasing diameter of each cavity is 

 understood when we recall the development of the organ and the tubes leading to it. 



FIG. 6. A horizontal section through the ventral projection of the organ which 

 is apparent in Figs. 7 and 8. The central part of this figure appears clear because 

 the section was quite thin and the cut parallel with the light portion of one of the 

 concentric layers. 



