440 Dr. Griffith on the Saccidi of the Poli/gasir-ica. 



and resembling in every respect the coloiu'ed granules which have 

 been described as visible in the gelatinous parenchyma of the 

 Hydra. AVith respect to the central canal, we have not in any in- 

 stance been able to detect it, or even any portion of the tube seen 

 in the figures, much less the branches leading from it to the ve- 

 sicles or stomachs, as they are called. Even the circumstances 

 attending the prehension of food would lead us to imagine a dif- 

 ferent structure ; witness, for example, the changes of form which 

 Enchehjs jnqja undergoes when it devours an animalcule almost 

 equal to itself in bulk, and is seen to assume a perfectly different 

 shape as it dilates its mouth to receive the victim, with which its 

 whole body becomes gradually distended. Such a capabdity of 

 talcing in and digesting a prey so disproportionate would in itself 

 go far to prove that the minute sacculi were not stomachs, as it 

 evidently cannot be in one of these that digestion is accomplished." 

 Professor Jones then says he considers that there is an analogy 

 between the organization of the so-named Polygastrica and of the 

 Hydra viridis. He also says, " that the vesicles becoming co- 

 loured by the coloured food given to the animalcules cannot be 

 considered as a proof of their being stomachs, as in the experi- 

 ments of Trembley, the granules circrdating in the body of the 

 Hydra became dyed with the juices of the animals with which it 

 was fed precisely in a similar manner." 



M. Meyen says* he never admitted the observations of M. Eh- 

 renberg, because in the first place " I never could see the intes- 

 tines which form the communication between the stomachs, and 

 likewise because I have observed, many years since, that the sup- 

 posed stomachs were moving in the interior of the body of many 

 species with great rapidity, in the same manner as the granules 

 which circulate in the joints of the Char a. I have often seen 

 Vorticellce with nine or ten large globules of indigo in the belly, 

 which always moved round a centre, and thus showed in the most 

 evident manner that they could not have a communicating canal be- 

 tAveen the stomachs provided with an oral orifice and an extremity 

 directed to the mouth." M. Meyen considers that the inner sur- 

 face of the first part of the canal is provided with cilia, which roll 

 up alimentary and colouring matters into the form of a ball. 

 When the ball has acquired the size of the stomach, it is expelled 

 by its other extremity and pushed into the cavity of the animal. 

 If solid substances do not exist in the surrounding liquid, then 

 the balls are less solid, and appear in the forms which they pre- 

 sent in the Infusoria existing in colourless liquids. " In this case 

 the balls are composed of a small number of particles, and prin- 

 cipally of a considerable mucous mass which unites them." 



* Annals, of Nat. Hist, vol.iii. p. 100; also inserted in Pritchard's ' Gen. 

 Hist, of Animalcules.' 



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