ZooL.— Vol. hi.] STEVENS— CILIATE INFUSORIA. II 



hom. ap. im. 1.15 mm.) the individual cilia can be traced 

 from the base to the edge of each membrane, either in liv- 

 ing or in fixed material (fig. 3, w\ tn^, m^, m^). 



Each individual cilium arises from a minute, clearly- 

 marked oval basal body about .2 /* in diameter, embedded 

 in the ectoplasm immediately beneath the pellicula, about 

 .5 yu- apart in the rows and .8 /ti from the adjacent row 

 (figs. 4, 6, 13, 14, 17). These basal bodies are espe- 

 cially well brought out by iron-h^matoxylin staining and 

 are in every respect comparable to those described for cili- 

 ated cells of Metazoa by Lenhossek (1898), Henneguy 

 (1898), Peter (1899), and others. 



The movement of the membranes is a rhythmical wave- 

 like vibration, starting at their base, the four membranes 

 waving in unison, the strongest and most constant move- 

 ment being on the left ventral side. The inner membrane 

 is sometimes seen tightly clasped upon the material to which 

 the animal is attached, while the other three and the velum 

 vibrate in unison. As these membranes are in constant 

 motion in life, and are the last part of the body to cease 

 moving, the various phases of their vibration are often 

 beautifully preserved in fixation (fig. 8). No such lack of 

 coordination as Wallengren describes was observed when 

 the membranes were more or less split up into cilia or 

 groups of cilia. 



In attempting to isolate the cilia, as has been done for 

 the ciliated cells of the alimentary tract of Anodonta by 

 Peter (1899) and others, the attachment disc was several 

 times severed from the oral disc at different points along 

 the neck. In these cases, the disc swam forward in the 

 water or moved along the glass exactly as under normal 

 conditions. This, together with the fact that the ciHa 

 vibrate after the pellicula and the general body entoplasm 

 are nearly or quite dissolved away by macerating agents, 

 may be cited as additional evidence that the kinetic center 

 of ciliary motion is to be found in the basal body or in the 

 basal body plus the cilium. 



