SENSORY EPITHELIUM OF PHARYNX AND CILIATED 

 PITS OF MICROSTOMA CAUDATUM. 



WM. A. KEPNER AND W. H. TALIAFERRO, 

 UNIVERSITY OF VIRGINIA. 



For more than four years the senior writer has been able to 

 collect Microstoma caudatum Ldy. from a little ice pond at the 

 eastern border of Charlottesville, Va. These animals during the 

 late autumn and on into early winter are frequently found 

 sexually mature; all that we have found in such condition proved 

 to be females. A mature female is indicated in our first figure, 

 plate I. No males have been recognized by either of us. 

 Many specimens have been sectioned and their sections studied 

 in series. These studies have shown that the sexually mature 

 individuals were not hermaphroditic. 



Specimens have been fixed in hot aceto-sublimate, Bouin's 

 fluid, and chrom-aceto-formalin mixture. In all cases the last 

 medium has given us the best results. We think it highly 

 important that the specimens be handled individually in fixing. 

 Our studies of the histology of the ciliated pits have been based 

 upon material fixed in chrom-aceto-formalin for twenty-five 

 minutes. Specimens were then rinsed in two or three changes of 

 tap water and carried through to paraffin. Sections were made 

 from three micra to ten micra thick. Iron hsematoxylin with 

 Bordeau red as a counter stain was employed. 



Microstoma caudatum Ldy. has a spindle-shaped'body measur- 

 ing from 750 micra to 1.5 millimeters in length. Its anterior end 

 is more rounded than the pointed, posterior end. The entire 

 surface is highly ciliated. The mouth, leading into a conspicuous, 

 ciliated pharynx or oesophagus, lies on the ventral side about 

 one sixth of the length of the body posterior to the anterior end. 

 No eyes or "eyes-spots" have been observed by us. The 

 ciliated pits lie dorsal to the mid-lateral surface of the body a 

 little anterior to the mouth. These organs together with the 



pharynx can be closed or distended. When the animal is testing 



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