. EXPLANATION OF PLATES 

 PLATE 27 



Camera lueida drawings of a series of transverse sections of Balantidium coli 

 (Malmsten). The series begins at tlie anterior end and progresses posteriorly 

 about one-third the length of the organism. X 1000. 



Fig. 1. This section shows dorsal portion only of peristome. The adoral cilia 

 are removed showing their basal granules clearly. 



Fig. 2. A portion of the oral plug is shown witli the cireumoesophageal fiber 

 and the connected oral plug fibers. The deeply-staining region between proto- 

 plasm of oral plug and the surrounding ectoplasm, so marked in this individual, 

 is rarely found. 



Fig. 3. The continuation of cilia over the ventral lip and down into the cyto- 

 stome are to be noted particularly; the beginning of the motorium on the 

 (reader's) left of the cytostome; and the connection of the adoral ciliary fiber 

 with the motorium. 



Fig. 4. In this figure the cilia of the cytostome give the appearance of mem- 

 branelles; the cireumoesophageal fiber makes connection with the motorium. 



Fig. 5. This shows the beginnings of the enlargements of the adoral ciliary 

 rootlets. 



Fig. 6. Here the oesophagus is completely siirrounded by the enlargements 

 and radial fibers may be seen arising from some of them. 



Fig. 7. The extreme posterior tip of the motorium appears wthin the circle 

 of enlargements; the dorsal half of this section is through the endoplasm. 



Fig. 8. This section is posterior to the adoral apparatus with the exception of 

 the rootlets of the adoral cilia which in cross-section can not be distinguished from 

 the granules of the endoplasm. 



[298J 



