642 DESCEiFTioN OF ISotatoria. 



external promiueut organ, tliougli some protrude the teeth in a 

 pincer-like manner. Tlie nutritive apparatus is a muscular oesopha- 

 geal head, having single-toothed jaws; an oesophageal tube, very 

 short, except in D. lacustris ; a simple conical alimentary canal in 

 six species ; and a constricted one, or stomach, in two species. In 

 all, two pancreatic glands are present, which, in D. lacustris, are 

 long, cyliudi-ical, and two-horned; in the rest they are spherical. 

 The ovarium, in D. lacustris, is band-like ; hi the others, like a ball ; 

 contractile vesicles are observed in four species ; sexual glands in 

 tln-ee. No species is viviparous; none carry their egg hanging to 

 them ; transverse vessels are seen in three species, and in one a 

 vascular net- work at the head ; tremulous gills are found in three 

 species, in two of which they ai'e evidently attached to the sexual 

 glands. The nervous system is more especially developed in D. 

 lacustris, but indicated in all the species by the coloured eyes. (For 

 observations on this genus, vide ante, p. 626.) 



'DmiMTHk lacustris. — Body stout, oval, crystalliae; the front straightly 

 truncated ; foot suddenly attenuated, in length one-fourth of the 

 body ; the toes one-third the length of the foot. The transparency 

 of this animalcule is often a great hindrance to the discrimination 

 of its internal organs, though they are very large ; the superficial 

 skin is delicately shagreened. Fig. 403 represents a side view (left) 

 of this interesting animalcule, with a Lynceus (see Microscopic 

 Calinet, plate vii.) in its stomach; its curious internal organization 

 is clearly depicted. Often found in green-coloured water. (l-70th.) 



D. grandis. — ^Body long, slender, and cyliudrical, obliquely trun- 

 cated anteriorly; toes straight, longer than the stout foot. The 

 forked central cacculus, between the two ocalar ganglia, is remarkable. 

 Fig. 404 is a side view (right) of an extended animalcule ; fig. 405 

 another, contracted, with the jaws pushed out. Length l-120th 

 to l-72ud. 



D. forcipata (Vorticella vermicular is, Cercaria forcipata et E. vernii- 

 cularis M.) — Body cylindrical, slender, obliquely truncated anteriorly; 

 toes decurved, and longer than the stout foot. Length 1-llOth. 



D. (?) aurita {Vorticella caniciila, M.) — Body cyliudrical, slender; 

 front straightly trimcated, auricled; foot suddenly constricted, toes 

 small. The ticinulous oigan (heart) observed bj- Corti \vas merely 



