442 Dr. Griffith on the Sacculi of the Pohjgastrica. 



hility of the oesophagus or common canal, such as we observe in 

 the boa constrictor, which becomes in hke 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 mo\-ing, and apparently 

 rotating through the general ca\ity of the animal. But the pe- 

 ristaltic wave-like undulations of a common connecting canal, by 

 di'awing them successively in and out of focus of the observer, is 

 quite sufficient, and very likely to occasion the deceptive appear- 

 ance of their circulatory movements. If these stomachs were ac- 

 tually separate and closed sacs imbedded in the transparent gela- 

 tinous plasma of the animalcule and endowed with a circulatoiy 

 movement, it is inconceivable that they should commonly present 

 the characteristic arrangement which Ehrenberg has described 

 and figured in particular species ; as for example in the Vorticella, 

 a circular arrangement, or the wa\T disposition in Leucophrys ; 

 yet such a constancy in the arrangement of the assimilative sacs 

 in these genera is the result of my exjierience. Add to this, if they 

 have not orifices of communication with the alimentary tract, the 

 difficidty of accounting for the rapid and ready transmission of 

 the coloured aliment into their interior without the sim-ounding 

 parenchyme being stained.^^ 



In support of the views of Prof. Ehrenberg I refer the reader to 

 vol. ii. p. 121. of the 'Annals,^ wherein is contained an account of 

 a discussion between this indefatigable observer and Prof. Jones. 

 It will there be fomid that Ehrenberg considers the objection of 

 Prof. Jones's not having been able to detect the stomachs in one 

 or two instances as not sufficient to biing into doubt " the mass 

 of relations which have been gradually established after many 

 years of observation." ^Moreover, Prof. Ehrenberg says that 

 Paramecium Aurelia is unfavourable to such obseiTation, and that 

 he himself has not been able to recognise the alimentary canal in 

 all the species of the various genera. The Berlin Prof, says he 

 had seen the circular motion of Prof. Jones, and states that '* the 

 great contractility of the body of the animalcules was, to less 

 practised observers, not seldom a cause of enigmatical phseno- 

 mena, of which continued patient observation of the object would 

 gradually bring the explanation. Thus at times the intestinal 

 canal of the animalcule extends at the expense of the ventral sacs 

 so far, that it occupies the whole space of the body, and then the 

 devom-ed substances, veiy similar to the ventral sacs, circulate in 

 the whole body." He then gives three sketches of Loxodes Bur- 

 saria, wherein the first represents the animalcule in its ordinary 

 state, \\'\i\\ the alimentary canal and sacculi ; the second, where 



