BPE5TEB OX T1IK ARRANGEMENT OF THE RHIZOPODA. -ti\7 



II. Eadiolart.v. Incipient dillerenl iati.m of ,the protoplasmic, 

 Bubstance into endosarc and ectosarc, the former Bemi-nuid and gra- 

 nular, the latter more tenacious and pellu< id ; a aucleua and 



tile vesicle; paeudoppdia rod-like, usually I o to 



point, composed of the pame substance as the ectoaarc, exhibiting 

 little diapoaitiou either to ramify or to coaleace, haying a more or 

 less regular radiating arrangement, and not Bhowing any conatant 

 circulation of granules in tjheir Bubatance, although a movement of 

 particles adherent to their exterior is often to be diatinguiahecl The 

 type of thia order is Actinophrys, constituting, with its immediate 

 allies, the family Actinoplivijna ; but the Order also includes the 

 Acanthomcfrina, Polycystina, and Thalassicollina, by the last of 

 which this group is connected with the Sponges. 



III. Lobosa. More complete differentiation of the protoplasmic 

 substance into endosarc and ectosarc, the former being a slightly 

 viscous granular liquid, and the latter approaching the tenacity of a 

 membrane: a nucleus and contractile vesicle ; pseudopodia few and 

 large, being in reality lobose extensions of the body which neither 

 ramify nor coalesce, having well-defined margins, and not exhibiting 

 any movement of granules on their surface, the circulation in their 

 interior being entirely dependent on the changes of form which the 

 body undergoes as a whole. This Order is composed of but a single 

 family, the Amoebina ; and it is the one which presents the nearest 

 approximation to the classes Infusoria and Gregarinlda. 



Having thus explained what I conceive to be the true relations of 

 the Foramixifera to other Ehizopods, I purpose now to state the 

 views to which I have been led by the same mode of enquiry, in re- 

 gard to the classification of that group. And in the first place, it is 

 requisite to examine what is the physiological value of the separation 

 of the Monolhalamous, or Unilocular, forms from the Polythalamous, or 

 Multilocular, — a separation which has been hitherto adopted by all 

 systematists as one of primary importance, although Professor Keuss 

 has lately expressed himself doubtfully as to the correctness of its 

 principle. 



There can be no doubt that, in common with all the lower forms 

 of animal as well as vegetable life, the Riiizopoda. tend to multiply 

 by a separation of continuously-growing parts of their bodies, which 

 may take the form either of fission or of gemmation, according as the 

 original body undergoes subdivision, or as it puts forth an extension 

 which eventually detaches itself. Among the Foraminifera proper, 

 whose bodies are enclosed in unyielding shells, multiplication by 

 fission cannot take place, except in that eari ice in 



which the shell is not yet consolidated ; hut extension by gemmation 

 may go on without limit, the successively-formed gemmae usually 

 remaining in connection with each other and with their slock. The 

 progressive growth of the sarcode-substance caiiaea a portion of it to 

 project beyond the aperture of the shell ; and thja projecting portion 



