452 Dr. G. C. Wallicli on Amoeba villosa 



certain Foraminifera. In crushed specimens the septal plate, and 

 its aperture (which is situated at the dorsal side of the tubular 

 expansion) may readily be seen. Fig. 13 exhibits a somewhat 

 different shape, but no material difference in the composition or 

 general character of the test, as is evident from the construction 

 of that portion around the aperture, of chitinous pellets iden- 

 tical with those in the previously described variety. So that 

 whereas in one form we observe a decided tendency to assume a 

 character not ordinarily met with in any of the freshwater Rhi- 

 zopods, in the other we have presented to us, in the same indi- 

 vidual, a combination of characters on each of which it has been 

 thought expedient by some writers to found as many distinct 

 species. Nay, more than this, if the principles so admirably 

 enunciated by Dr. Carpenter * are those on which alone a na- 

 tural classification of the Rhizopods can be built up, we must at 

 once and for ever discard as Ordinally distinctive those differ- 

 ences which do not involve the animal that forms the test, but 

 only the test that is formed by it. It is, I conceive, impossible 

 to examine the pseudopodia and other soft parts of Arcella and 

 Difflugia, without at once perceiving their generic identity. It 

 is equally impossible to examine those of Euglypha, Lagynis f, 

 and some allied but less-known forms, without perceiving that 

 the animals producing them are also generically identical. At 

 most, mere modifications in the shape and proportionate quanti- 

 ties of the organic and inorganic elements that enter into the 

 formation of the shell ought only to be employed to discrimi- 

 nate between species. But even here we may go a step too far, 

 as is shown by the varieties of Difflugia, unless we start with the 

 admission that the separation of such forms is simply a matter 

 of convenience. 



In conclusion, it only remains for me to state that, whilst 

 courting the scrutiny on which the acceptance of every new 

 scientific fact very properly depends, I have for the present pur- 

 posely abstained from the extension of my hypothesis beyond 

 those lowest forms of animal life to which reference has been 

 made — my desire in so doing having been to dispel, with as little 

 delay as possible, what I cannot regard otherwise than as a most 

 unsatisfactory and untenable view of the mystery of Sarcode. 



* Introduction to the Study of the Foraminifera. 



\ If we include those forms of decided Euglypha to which Schlumberger 

 has given the distinct specific appellations of Cyphoderia, Sphenoderia, 

 and Pseudodifflugia, the force of tlie observation becomes doubly manifest. 



Errata in paper on Amoeba in the ' AnnaW for May : p. 366. 

 Twelfth Une from bottom, dele " not." 



Eleventh hue from bottom, instead of " but is " read " and not." 

 Seventh line from bottom, dele " not." 

 Page 369, end of twentieth line from top, dele " comma." 



