464 Dr. Wallicli 07i the Rhizopods. 



belong to Nebela collaris^ calls the peculiar elements colloid 

 disks and plates. He remarks that tliey are derived from 

 the animal, and not directly from the medium in which it 

 lives. He supposes, however, that they are formed through 

 the coalescence of diatoms and other mineral elements with 

 the chitinoid basal substance of the shell, which then undergo 

 metamorphosis into all the colloid forms that occur." 



Before proceeding with my observations on the ^^Nebelce " 

 I must make some comments upon the above statement in 

 relation to the whole of the series of transitional and meta- 

 morphic forms referred by me to the genus Difflugia. The 

 first point on which I lay emphasis is the extraordinary fact 

 that this short paragraph contains nearly if not quite all 

 the information Prof. Leidy has vouchsafed to publish concern- 

 ing i\\e. grounds on which the conclusions in question were based. 

 The second point is one upon which I would lay still greater 

 emphasis, namely, the fact that, without any explanation what- 

 ever on Prof. Leidy's part, the whole of the metamorphic forms 

 described and figured by me were bodily consigned^ as in the 

 case of Diffiugia symmetrica^ to a new genus. For, with 

 exception of the short paragraph above quoted, from the first 

 page of his work to the last, he has abstained from drawing 

 attention to my reasons for maintaining that influences in 

 nature extrinsic as regards the animal, serve in a principal 

 degree to determine the external structure and constitution of 

 the ectosarc of the naked Phizopods, and notably the external 

 structure and constitution of the tests of the testaceous forms. 



On the other hand, he has several times gone out of his 

 way to direct attention to conclusions of mine whicli he leaves 

 it to be understood he considers erroneous, but which appear 

 erroneous only because he has completely misrepresented 

 them. That this is no exaggeration will be seen on reference 

 to pp. 150 and 151 of his work, where, in the course of four- 

 and-twenty lines, he gives the subjoined two versions of the 

 same inaccurate statement in relation to the Nebelce : — 



" The series of specimens represented by Dr. Wallich in 

 figs. 27 to 33, pi. xvi., vol. xiii. Ann. & Mag. Nat. Hist, for 

 1864, and described as transition forms of Dijfiugia symme- 

 trica, appear to me to pertain to the same animal as Nebela 

 coUarisy 



" Dr. Wallich, in referring to the structure of the shell of 

 the transitional forms of Diffiugia symmetrica, which, as 

 previously intimated, I suspect to belong to Nebela coUaris, 

 calls the peculiar elements colloid disks and plates." 



And yet a few pages before, namely at p. 145, he had 

 already stated in his definition of the genus Nebela, that 



