Abbreviations used on Plates 



In each figure, the mognification mark equols one micron. 



Fig. 1. Sagittal section of a very nearly mature stenotele. Newly de- 

 scribed structures are the enlarged head of the tubule (HD), hook of the 

 tubule (HK) and the enlarged bulbous base of the spines (arrows). The 

 unique appearance of the material in the tubule head should be noted. 

 XI 7,000. 



J 38 



