Dr. Wallich on the Rhizopods. 319 



furnished with shell-like or chitinoid coverings, that attention 

 is specially invited. The question of subdivision into orders, 

 although of primary importance as -regards the basis of every 

 system of classification, being in reality of secondary im- 

 portance for the purpose now in view, is imported into it 

 solely in order to determine the position of Gromia^ con- 

 cerning which, as will be hereafter seen, there would still 

 appear to be a great deal of misconception. 



According to Dr. Carpenter, the subdivision into orders 

 may be best accomplished by taking as a basis " those 

 structural characters which are most expressive of physio- 

 logical difference in the form^ 'proportions^ and general 

 arrangement of the pseudopodial extensions; for notwith- 

 standing their unrestrained polymorphism, the Rhizopods 

 present three very distinct types of pseudopodian confor- 

 mation, to one or other of which they may all be referred, 

 the group thus formed being eminently natural.'''' Dr. Car- 

 penter then proceeds to say that " in cases in which the 

 differentiation into ectosarc and endosarc has proceeded 

 furthest, so that the body of the Rhizopod bears the strongest 

 resemblance to an ordinary cell, as is the case with Amoeba 

 and its allies, a nucleus may be distinctly traced • in those, on 

 the other hand, in which the original protoplasmic condition 

 is most completely retained (as seems to be the case in Gromia 

 and with the Foraminifera generally), no nucleus can be 

 distinguished " *. 



In Dr. Carpenter's classification Gromia is consequently 

 made the type of his lowest or Reticularian order, and is 

 associated in that order with the Foraminifera only. The 

 same basis of classification would seem to have been a,dopted 

 by Prof. Huxley in his " Hunterian Lectures on the Inverte- 

 brata," delivered in 1867, when he described the Foraminifera 

 as a group of Monerozoa containing some of the very 

 simplest forms of life, one of the simplest of Foraminifera 

 being Gromia, a jelly-like mass with extensile pseudopodia 

 enclosed in a horny shell, differing from the imperforate Milio- 

 lidaj and Lagenidse only in having a membranous or horny 

 shell t. 



In the Ann. & Mag. Nat. Hist, for June 1863 it was 

 pointed out by me that the nuclear body with its capsular 

 investment made its appearance for the first time in the two 

 highest orders, and not in the lowest, which in my system. 



* ' The Study of the Foraminifera,' 18G2, pp. 14 and 16. 



t " Roy. Coll. Surgeons : Hunterian Lectures by Prof. Huxley, F.R.S., 

 on the Invertebrata." TAbstract.) Quart. Journ. Microsc. Science, 

 1868. 



22* 



