Dr. Wallicli on the UMzopods. 323 



tributing the previously so-called typical characters of its 

 pseudopodia to its transitionary tendency, these characters, 

 when taken in conjunction with the vastly more important 

 presence of the nucleus and contractile vesicle, which alone 

 indicate the true systematic position of the organism, proved 

 at once that the Eeticularian type, as well as every other 

 pseudopodian type, could no longer be received as indicative 

 of physiological advance, and consequently could no longer be 

 considered of any practical value in the subdivision into orders 

 of the various families of Rhizopods. 



Having thus shown how the case stood in the year 1877, 

 it will now be necessary to redirect our attention to the years 

 1863-4, when I called attention for the first time in the 

 ' Annals ' to the occurrence in this country and elsewhere of 

 an extensive and highly interesting series of testaceous 

 Rhizopods Avhich, with three exceptions to be referred to 

 hereafter, had not previously been described and figured by 

 any other writer. Two of these excepted forms were in- 

 cluded in Ehrenberg's famous work ' Die Infusionsthierchen,' 

 published in 1839, but without any observations beyond a 

 somewhat imperfect description of their external characters, 

 due no doubt to the inferior nature of the microscopic appli- 

 ances then available. In these circumstances, and in entire 

 ignorance of the fact just stated, I described and figured the 

 two forms in question, together with the remainder of the 

 really new and typical varieties of Diffiugia which had been 

 discovered by me in India and in this country, in the ' Annals ' 

 for June and December 1863 and March 1864. 



The whole of these forms, which, for reasons to be presently 

 given, were referred by me to the genus Dijfflugia, threw an 

 entirely new light on the relations borne by the animal to the 

 shell, or (as it ought to be called in the case of the testaceous 

 Rhizopods) the test *, which the animal inhabits but is 

 only to a certain extent instrumental in constructing. The 

 clue to this most interesting and till then novel fact had 

 revealed itself to me in some of the living organic forms 

 obtained in soundings made in the North Atlantic in 1860 on 

 board H.M.S. ' Bulldog ' f, the tubes of certain minute 



* It would rid us of a very troublesome source of uncertainty and con- 

 fusion were the term shell conlined to the shells of the Foraminifera ; skele- 

 ton or framework to the internal siliceous structure of the Polycystina, 

 Acanthodesmidse, and Dictyochidse ; and tests to the more or less chitinoid 

 coverings of the Difflug'idEe, Lagynidae, and allied forms. As it is, these 

 terms are employed indiscrimioately and without any definite meaning 

 attaching to each. 



t 'The North- Atlantic Sea-bed,' G. C. Wallich, 1862, part 1, pp. 14G, 

 147 ; and * Biology of Qlohigerina,' 1876, pp. 11 and 12. 



