OF MICR O- OR G AN! SMS. 9 



gous to that of the rotifers; it produces eddies in the 

 water and thus causes the flow of foreign bodies to the 

 mouth: these animals have the rest of their bodies 

 covered with fine cilia. In the Hypotricha the cilia 

 are located on the ventral surface of the body and aid 

 in locomotion. In the Peritricha, they form a cir- 

 cular or spiral row on the anterior part of the body, 

 and lead to the mouth. This is observed in the Vor- 

 ticels, sessile species which have no other cilia than 

 those which are used for the prehension of food; the 

 rest of the body is bare. 



Much has been said about the morphological signif- 

 icance of vibratile cilia; several micrographists have 

 held that the cilia are attached to the enveloping mem- 

 brane only, and have no connection whatever with the 

 protoplasm. That was notably the opinion of Robin; 

 it is entirely wrong. The cilia are never simple pro- 

 longations of the cuticle; they have their root in the 

 protoplasmic substance; they pass through orifices in 

 the cuticle, which consequently is pierced by a multi- 

 tude of small holes. Engelmann, in recent observa- 

 tions, has been able to trace the extremity of the vibra- 

 tile cilia into the interior of the protoplasm; he made 

 this observation on the marginal cilia of the Stylo- 

 nichia; from each of these threads he has seen sep- 

 arate a pale fibre, which moves along almost directly 

 beneath the cuticle in a direction perpendicular to the 

 lateral edge of the body; towards the median line of 

 the ventral face the fibres are often laid bare, because 

 the body of this Infusory voids its protoplasmic sub- 

 stance; there the fibres have the aspect of tightened 

 threads. Engelmann sees in this observation a con- 

 firmation of the opinion that the bodies of infusoria 

 are formed of one single cell, because, according to 



