I'OLYGASTKIA. 23 



a long extensile neck, as in Lacrijmaria ; in some monads, if Ehren - 

 berg have rightly interpreted its presence and position, it is pro- 

 vided with a long tentacle or a pair of tentacles {p'g. 11. a.) ; it has a 

 conspicuous fringe of cilia in some Polygastria {Jig- 13. «.) ; in other 

 species it is unequivocally armed with a curious dental apparatus, 

 consisting of a series of long, slender and sharp teeth, arranged side 

 by side, in the form of a cylinder, as in Chilodon and Nassula 

 {Jig. 14. a, a). 



Later Microscopists have failed to detect the mouth or the canals 

 converging towards it from the green globules, which canals Ehren- 

 berg has described and figured in the constituent monad of the 

 Volvox glohator{fig. 11).* Sieboldf refers, indeed, the Volvoci7icB to 

 the same group of the Vegetable Kingdom as the Closterince and 

 BacillaricB ; and he cites the unusually large species of the genus . 

 Opalina (0. Ranarum), parasitic in the intestines of the Frog, as 

 affording indubitable evidence of the absence of any mouth, and 

 of the power of these astomatous Infusoria to absorb fluid nourish- 

 ment by generally diffused surface-pores, as shown by the bile- 

 stained contents of their body. In certain Astomata, with long 

 cilia or filaments, e. g. Actinophrys Sol, when a prey is brought 

 within their reach the filaments incline towards and bend over it, 

 intercrossing each other and pressing the prey to the surface of the 

 animalcule. That part of the surfiice yields ; the prey, whether it be 

 a smaller animalcule or plant-sporule, sinks into the substance of the 

 body, which closes over the prey without leaving any trace of its pas- 

 sage : functionally such passage performs the office of a mouth ; just 

 as the vacuolae in the central plasma, which receive the nutriment so 

 taken in, perform the office of stomachs : but neither such mouths nor 

 stomachs have proper parietes or a permanent existence J: and the same 

 may be said of any part of the external parietes of the animalcule 

 through which insoluble or indigestible parts of the food are extruded. 

 In the higher forms of the Polygastria provided with a determinate 

 mouth armed with teeth, the larger objects of food are seized and 

 bruised by them: the dental cylinder first expands in front to 

 receive the morsel, and, as this passes along, the cylinder contracts in 

 front and dilates behind, so as to push the food into the digestive cavity. 

 If such larger animalcules with unequivocal mouths be removed from 

 their native infusion to a drop of clear water, and after they have fasted 

 a few hours, a drop of the solution of pure indigo or carmine be added, 

 the fine particles of these colours will be greedily swallowed, and will 

 soon be seen to fill successively a number of pyriform or spherical 



* XL, tab. iv. fig. 1. 13. t X. p. 7. % XIX. p. 198, pi. xvii. 



c 4 



