POLYGASTRIA. 



21 



the animal. Ehrenberg has observed and figured certain definite 

 arrangements of these digestive sacculi, as well as of the alimentary 

 canal, to which he states that they are appended. In the Monads, 

 and many other of the more minute species of Polygastria, the sto- 

 machs are said to arise by separate tubidar pedicles from the common 

 dilatable cavity of the mouth itself (^fig- 9. h, b). Such species have 

 no intestine, no anus, and are said to be anefiterous. In others, where 

 the sacculi are aj^pended to an alimentary canal (^Polygastria en- 

 terodela Ehr.), that canal may be bent into a loop, and describe a 

 circle with the anus, opening near the mouth, as in Vorticella (Jig. 10.) ; 



or it may pass in a straight line 

 through the axis of the body, as 

 in Enchelis ; or form several 

 flexuous curves in its passage 

 from the mouth to the opposite 

 extremity of the body, as in Leu- 

 cophri/s(Jig.5.). But sometimes, 

 as in the Kolpodee, neither the 

 mouth nor anus is terminal in 

 position. 



It has been objected to this in- 

 terpretation given by Ehrenberg 

 of the nature of the sacculi which 

 receive and assimilate the nu- 

 trient molecules that certain spe- 

 cies, as the Enchelis pupa, will 

 swallow another animalcule nearly equal to itself in bulk, and 

 thereby undergo a total change in the form of its body ; but this 

 may only imply great dilatability of the oesophagus or common canal, 

 such as we observe in the boa constrictor, which becomes in like 

 manner deformed after gorging a goat or other animal much thicker 

 than itself; doubtless the little sacculi successively receive and digest, 

 like the stomach of the boa, the dissolved parts of the swallowed 

 prey. Then again it is objected that the sacculi are not fixed in 

 definite positions, but are seen constantly, though slowly, moving, 

 and api^arently rotating through the general cavity of the animal. 

 But the peristaltic wave-like undulations of a common connecting canal, 

 by drawing them successively in and out of the focus of the observer, 

 is quite sufficient and very likely to occasion the deceptive appearance 

 of their circulating movements. If these stomachs were actually 

 separate and closed sacs imbedded in the transparent gelatinous 

 plasma of the animalcule, and endowed with a circulatory movement, 

 it is inconceivable that they should commonly present the charac- 



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