130 DESCRIPTION OF [Polygastrica. 



FAMILY IV. VIBRIONIA. 



The animalcules of this family are distinctly or appa- 

 rently polygastric, but without a true alimentary canal. 

 In shape they are filiform, and, like the Monadina, are 

 incapable of changing the form of their body. They have 

 neither appendages or shell-like covering. They are 

 associated or linked together in thread-like chains, formed 

 by their imperfect mode of self- dividing, which takes place 

 in a transverse direction. Considering how much we 

 know of the organization of the family Monadina, we are 

 comparatively far behind in information respecting the 

 Vibrionia, and were it not that the cause of our ignorance 

 is manifestly attributable to the exceeding minuteness of 

 the individual animalcules, we might be justified in 

 imagining their structure to be more simple than in all 

 probability it really is. Their filiform and very delicate 

 bodies are not, as we have said, separate animalcules, but 

 formed of chain-like clusters, whose almost imperceptible 

 links are themselves (at first) single creatures. The 

 reasons to be assigned for arriving at this conclusion are, 

 that the clusters or chains have never any determinate 

 length, or number of members forming them, and that 

 they are sometimes so short as to be made up of not more 

 than two or three individuals, and only distinguishable 

 from the M. termo and crepusculum by their mode of 

 union, and peculiar, though not easily characterized, 

 movements. Hence all their organic relationships are to 

 be sought for in these minute portions of the chain. To 



