PLATE I. 



Fig. 1. Portion of a longitudinal section of the dorsal wall of the body, showing 

 the parent cells of the rhabditi and the position of the rhaluliti in the 

 hypodermis. X 900. 



" 2. Cross section near the lateral margin of the dorsal side, in a region 

 where there were no rhabditi, showing the hypodermis in its primitive 

 condition. X 000. 

 In Figures 1 and 2 the basement membrane did not take the stain. 



" 3. Longitudinal section through a region where there were many rhabditi 

 which have been removed by partial maceration, showing the modi- 

 fied condition of the hypodermal cells due to the crowding of the 

 rhabditi. X 000. 



" 4. Longitudinal section of ventral wall of body, showing a young parent cell 

 of the rhabditi, the nucleus almost filling the cell. The hypodermis 

 removed. X 900. 



" 5. Two parent cells of the rhabditi, from macerated material. X 960. 



" 6. Longitudinal section of ventral wall showing two stages in the develop- 

 ment of the parent cells of the rhabditi. Two small rhabditi have 

 already been secreted in the larger cell. The hypodermis removed. 

 X 900. 



" 7. Stage in the development of the parent cells of the rhabditi next older 

 than that shown in Figure 4. The cell has sunk deeper into the 

 tissues, and the nucleus is smaller in relation to the size of the cell. 

 Ventral wall of body, the hypodermis being removed. X 900. 



" 8. Longitudinal section of ventral wall showing one of the rhabditi in the 

 act of passing through the basement membrane. The hypodermis re- 

 moved. X 900. 



" 9. Showing the appearance of the rhabditi after having been acted upon by 

 picric acid. X 900. 



" 10. Longitudinal section of the ventral wall showing one of the parent cells 

 of the rhabditi filled with the rods. The remnants of another cell 

 represented by the nucleus and three rhabditi are seen close by The 

 hypodermis has been removed. X 900. 

 Owing to a mistake of the lithographer, the nuclei of the parent cell 

 (nl. rhb.) in Figure 10 are not represented as being granular, as they 

 should be. 



