644 DESCKIPTION OF [^Rotatoria. 



and the foot, are nearly three times the length of the body. This 

 species is distinguished from the following one by the greater length 

 of cm-hi ; by larger eyes, further removed from each other ; by a 

 distinct stomach, with a constriction separating it from the long 

 portion of the alimentary canal ; and, lastly, by its long oesophageal 

 tube. It is readily distinguished by its leaping movement whilst 

 swimming. Pig 408 represents one of these creatures emerging 

 from the egg, th.e cirrhi or styles being, as yet, soft : fig 407 is a 

 back view of a young specimen ; it shews the great separation of 

 the eyes and the styles, in the position they occupy when the animal 

 is swimming ; and fig. 406 is a side (right) view of a full-grown 

 specimen ; the styles are advanced, preparatory to leaping. Found 

 with Hydatina senta and Brachionus urceolaris. Length, without 

 ciiThi, l-140th. 



Teiasthka mystacina {Brachionus passus, M.) — Eyes close to- 

 gether; two anterior cii-rhi, or bristles; foot nearly double the 

 length of the body ; jaws very soft. Foimd iu water-tubs. Length 

 1-2 16th. 



T. hreviseta (Gosse.) — Body cylindrical; pectoral and caudal 

 spines each about one fifth of total length, and very slender. Length, 

 including foot, l-185th. Leamington. 



Gcnns Ratttjltjs. The rat Rotatoria. — Frdntal eyes, two ; foot 

 simple, styliform ; no cirrhi or beard. Several undefined rotary 

 muscles, an oesophageal head, without distinct teeth or oesophageal 

 tube, a simple conical alimentary canal, with two round glands, an 

 ovarium, and eyes, constitute the organization at present discovered. 



This genus Rattulus or Ratulus was established by Lamarck ; but 

 was subdivided by Ehrenberg who made two genera, Mastigocerca 

 and Monocerca, to comprise the animals described by Lamarck, and 

 reserved the term Rattulus for an animal placed by the latter among 

 Cercaria, and called by Miiller, Trichoda lunaris. The Mastigocerca 

 carinata (Ehr.) is described as loricated, and enters into the family 

 Euchlanidota, and Monocerca rattus without lorica, is placed among 

 the Ilydaiinoea ; but the beings described under these two appellations 

 represent but a single species, Ratulus .... The Monocerca licornis of 

 Ehrenljcrg would seem to be a distinct species, by reason of the horns 

 with wliich it ib armed iu front. 



