Astasiaea.] the infusoria. 151 



Family VI.— ASTASIAEA. 



This family is characterized by its members being poly- 

 gastric, and deficient of the true alimentary canal, appen- 

 dages, or lorica. They are furnished with a single aperture 

 to the body, and often a tail, and have the power of chang- 

 ing their form at pleasure. They afford as beautiful living 

 objects for the microscope as any that have ever fallen 

 under my observation. The tail may be considered as an 

 organ of locomotion, and the single proboscis of three of 

 the genera, and the double proboscis of one other genus, 

 are of the like description. It is probable that these latter 

 organs exist also in the genus Colacium, although they 

 have not been determined ; but in the Distigma there is 

 hardly a doubt of their absence. The vesicular cells have 

 been supposed to form a portion of the nutritive apparatus, 

 although it is not satisfactorily demonstrated by the appli- 

 cation of coloured food. Ehrenberg has, nevertheless, 

 noticed some manifestations of an artificial action having 

 been produced, as he observed green and red cells in the 

 Euglena viridis. Three genera in this family exhibit 

 signs of the hermaphrodite condition, whilst the other three, 

 Astacia, Distigma and Colacium, have only one kind of 

 structure, namely ova. In the Euglena there may be seen, in 

 addition to the green ova and seminal glands, a contractile 

 vesicle of a seminal description, and the large red visual 

 point in five of the genera affords evident tokens of a 

 system of sensation. What, hoAvever, may be deemed most 

 worthy of remark in this family, is, that in the species. 



