298 DESCRIPTION OF [Polygastrica. 



485. BuRSARiA pupa. The doll-like Bursaria. — Body 

 white, ovato-oblong, rather acute posteriorly, mouth 

 aperture inferior, and near the frontal apex {see Jig. 296). 

 Found in chalybeate water in Germany. Size 1 -280th. 



486. Bursaria flaca. The pale yellow Bursaria. — 

 Body ovato-oblong, often acute at the posterior extremity; 

 the mouth appears as a flat cavity immediately behind 

 the round brow. Found in bog water. Size 1 -140th to 

 l-96th. 



487. Bursaria nucleus. The almond-shaped Bursaria 

 has a small white ovate body, attenuated anteriorly ; ex- 

 tremities convex. Found in Rana temporaria and esculenta. 

 Size l-240th. 



488. Bursaria ranarum. The frog Bursaria. — Body 

 ovate, lenticular, and compressed, sub-acute anteriorly ; 

 the back and belly carinated, and often truncated poste- 

 riorly ; mouth inferior, situated near the frontal apex. Size 

 1-2 10th to 1-7 2nd. 



489. Bursaria (?) auranfiaca. The orange-coloured 

 Bursaria. — Body ovato-oblong, anterior obtuse, posterior 

 acute ; it has an ash-coloured spot near the mouth. Found 

 amongst oscillatoria. Size 1 -280th. 



Genus CXIII. Spirostomum. The snail Animalcules 

 have their bodies ciliated, the frontal region continuous, 

 mouth spirally shaped, devoid of teeth, but with a tremu- 

 lous flap. The cilii, which are disposed in rows, serve as 

 organs of locomotion ; those at the oblique frontal ridge 

 are longer, and form, as in Stentor, a S})iral wreath around 

 the mouth ; in S. ambiguum the brow^ and wreath are 

 remarkably long. Digestive cells, to the number of ninety, 

 have been demonstrated by coloured food, and its discharge 



