INFUSORIA. 



39 



dant in the fall. It may be said always to occur in these localities, together 

 witli a rotifer, Annrcea longis^nna, which has singularly long anterior and 

 ]josterior spines corresponding in number with those of the infusorian. 

 The resemblance is striking. Mr. J. Levic has recently found the same 

 forms together in Olton Reservoir, near Birmingham, England. 



The sjiecies of the remaining families have one or more flagella (usu- 

 ally one), with the body more or less clothed with cilia ; in some the 

 whole surface bears them, in others only a crown of cilia occurs at the 

 anterior end, the flagellum standing in the midst. Asthmatos cilko-is 

 (Fig. 36) exemplifies this structural peculiarity. This species occurs in the 

 mucus from the nasal passages of persons suffering from " hay fever," and 

 is held by Dr. J. H. Salisbury to be the cause of this distressing complaint. 



Fig 36 



matos ciharis, 

 raagnifaed 500 

 times. 



Order II. — CILIATA. 



The animalcules of this great order, as the name implies, possess cilia as locomotory 

 organs. Tliey are much more highly organized than the Flagellata, and many of the 

 forms included are generally better known, and are more 

 generally called to mind by the name Infusoria. Stein's 

 di\-ision of the order into suborders is as follows : Holo- 

 tricha, with cilia over the whole surface ; Heterotricha, ^^•itll 

 cilia distributed over the entire surface, having those near 

 or surrounding the mouth longer; Peritricha, cilia mostly in 

 a wreath about the mouth ; and Hypotricha, with cilia on 

 the ventral surface only. 



Sub-Order I. — Holotricha. 

 A common type of the first sub-order and of the family 

 Paramecid.« is Paramecium aurelia (Fig. 37). It occurs 

 in hosts in vegetable infusions, stagnant pond-water, etc. 

 These active, elongate, animalcules are alike the delight of 

 the amateur microscopist and the joy of the veteran inves- 

 tigator ; it is to him what the frog is to the general anato- 

 mist and physiologist. It was made for investigation ; the 

 comparatively large size and trans]iarent body fit it admirably 

 for study, and it has not been neglected. The anterior third 

 of the body is somewhat flattened and twisted, so that the 

 flattened face resembles a living figure of 8 ; near the middle 

 of the ventral face — at the posterior extremity of the 8 — 

 the mouth is situated. The rejectamenta issue at a point 

 aliout half-way from the oral aperture to the posterior ex- 

 tremity of the body. There are two contractile vacuoles near 

 the extremities. When expanded they are round, but when 

 contraction takes place there appear fine radiating streaks, 

 M'hich, as the main portion decreases, sraduallv broaden ^'°' 37. — Paramecium aurelia, 



,., , ^, c . , , •' ' greatly enlarged. 6, c. Con- 



untu, when the toriner is nearlv invisible, tbev are extended tractile vacuoles, a. Mouth. 



1 iir ^1 1 ,,.,,", T , e. CEsophagus. o, i. Food vac- 



over halt the length ot the bod}-. It has been suggested ""'«s. h. Nucleus, m. Endo- 



