46 Infusoria : What are tlwy ! 



and handsomest representatives of the Infusorial class as 

 exemplified by the Stentors or " Trumpet Animalcules," and 

 the genera Bursaria and Spirostojmnn. In the third order, 

 that of the Peritricha, the cuticular ciliary series is entirely 

 suppressed, a spiral or circular series surrounding the 

 anterior border, while a second supplementary girdle is 

 occasionally developed towards the central or posterior region. 

 This division is interesting as containing the exceedingly 

 elegant " Bell Animalcules " or Vorticellidge, all characterised 

 by their normally sedentary habits, and being, as in Vorticella 

 proper, attached singly to their fulcra of support through 

 the medium of a complex retractile pedicle, or, as in the case 

 of Carchesium and Ejnstylis, building up through repeated 

 subdivision extensive tree-like colonies. Other Vorticellidse, 

 such as Cothurnia and Yaginicola, inhabit elegant stalked or 

 sessile protective sheaths or loricae, whose orifices are some- 

 times guarded by opercula or lid-like structures. Some 

 one or more members of this very characteristic group reward 

 a dipping fi-om any weed-grown pond. The fourth and last 

 group of the Ciliata is known as the Hypotricha ; it includes 

 all infusorial forms which, like Euplotes, Stylonijchia, and 

 Oxytricha, have locomotive cilia developed only on the lower 

 or ventral surface of the body. These cilia are usually 

 diversely modified in the same individual, taking the form of 

 setas, styles, or uncini, and constitute veritable ambulatory 

 organs wherewith their possessors literally walk, insect-wise, 

 over the surface of submerged objects. 



The animalcules comprised in the relatively small group of 

 the Tentaculifera — including Acineta, Podoj^hrya, and their 

 allies — were for a long while regarded as embryonic con- 

 ditions only of certain Ciliata. The tables have now, how- 

 ever, been so far turned that not only are they recognised as 

 constituting an independent series, but they are also shown 

 to originate from ciliated germs, and consequently represent 

 an even more highly developed class than that of the Ciliata. 

 All the Tentaculifera are distinguished by their possession of 

 tubular, and mostly retractile, tentacle-like appendages, which 

 are utilised by the free forms for locomotive purposes, but 



