66 INFUSORIA. 



In Opkryoglena flavicans a remarkable body 

 termed the " watch-glass-like organ " has been 

 recentW observed by Lieberkiihn. It is colourless, 

 transparent, homogeneous, and immovable, with 

 its convex side turned towards the pigment spot, 

 whilst its concave side is directed towards the 

 point of the head. It has also been detected in 

 Bursaria flava. Its use (as also that of the pig 

 ment spot) is unknown. 



9. Urticating organ*^. — In the cortical layer 

 of Bursaria, certain peculiar fusiform bodies or 

 ' trichocysts ' have been detected, and from these 

 Prof. Allman states that he has observed the emis- 

 sion of minute filaments which bear some resem- 

 blance to the urticating organs of the fresh-water 

 polype. They occm-, also, in other Infusoria. 



10. liO€»oiiiJ>tlve orgaes. — In by far tho 

 greater number of Infusoria locomotion is effected 

 by the vibratile movements of the peculiar hair- 

 like appendages usually denominated cilia. The 

 cause of these movements is at present unknown, 

 nor is it certain vv^hether they are dependent 

 upon volition. The cilia vary in position and 

 mode of arrangement among the several members 

 of the group. Thus, in Enclielys they are scat- 

 tered, apparently without order, over the entire 

 surface of the body ; in Vorticella and Vaginicola 

 they are confined to the neighbourhood of the an- 

 terior extremity, whilst in Paramecimn and its 

 allies they are disposed in a series of regular rows, 

 parallel to one another. In other Infusoria they 

 either surround the entire marg-in of the flattened 

 body, or encircle it in the form of an oblique 



