234 GENERAL HISTORY OF THE INFUSORIA. 



to be possessed of a nucleus. On the other hand, a large number of species 

 are able to produce new individuals by the mere detachment of a portion of 

 theu' sarcode substance, — an act in which no nucleus is concerned, whereas 

 in cell-propagation by fission a preparatory section of the nucleus appears a 

 necessary process. In the Ehizopoda, therefore, we may conclude that, in 

 the language of Professor Owen, " the spermatic force " is diffused through- 

 out their entire substance, and not, as it were, concentrated in a particular 

 organ or nucleus. 



The question respecting the nature of the many-chambered Foramin'ifera, 

 whether thej" are to be considered single individuals or colonies of animals, is 

 elaborately examined by Schultze, who comes to the conclusion that the 

 inhabitant of each shell is a single animal. Ehrenberg is the supporter of 

 the opposite view ; but Schultze shows that several structural details given 

 by him, upon which the colony-theoiy is partly established, are erroneous, 

 and that it is one common connected substance which occupies each and every 

 chamber. Prof. Williamson {T. M. S. 1851) has the following pertinent 

 observation on this colony-theory. Speaking of the Orbiculhia adunca, he 

 says — '' The attempt to isolate the various portions, and to raise each portion 

 to the rank of an individual animal, even in the limited sense in which we 

 should admit such a distinction in the polypes of a Sertidaria or of a Gorgonia, 

 appears to me wholly inadmissible." Moreover, the soft-structiu'es being 

 devoid of visible organization, " the whole animal wiU be very httle raised 

 above the Polypifera, only possessing a symmetrical calcareous skeleton, 

 which is at once both external and internal " (/. e. the Porifera). 



Of THE Affinities of Ehizopoda. — That the Ehizopoda constitute a class 

 of animalcules distinct from every other is evidenced by their characteristic 

 \T.tal structure and phenomena, their power of producing their like, their 

 growth, theii' faculty of digesting and appropriating nutrient matters, and by 

 the ascending stages of development seen among them, advancing fi'om the 

 simple Amoeba to the compound testaceous Cristellaria and Polystomella. 



In the natiu'e of their animal portion they resemble Cihated Protozoa ; it con- 

 tains similar vacuolae and graniiles, and also a contractile vesicle. On the other 

 hand, they differ from them in having no definite outline to the animal tissue 

 boimded by a hmiting membrane or integument, and particularly in possess- 

 ing no cilia, which, as locomotive organs, are replaced by the pecuHar and 

 characteristic pseudopodes. In variabHity of outline an approach is made to 

 Ehizopoda by some genera of the heterogeneous family, Enchelia of Ehi'enberg ; 

 but they never exhibit any such changeable character as the siu'face of the 

 former, never protrude similar variable processes, nor present a circulation 

 of granules. The Dinohryina might perhaps be cited as affording an example 

 of a considerable variability of form ; but our knowledge of this family is too 

 incomplete to render analogies based on it of value. 



The affinity between Ehizopoda and Phytozoa is no closer. Some of the 

 latter can greatly modify their form in mo\dng ; but in none does this partake 

 of the character and extent of the variability exhibited by Ehizopods. More- 

 over in none are variable processes found, but in general one or more elon- 

 gated cilia or filaments, which, by their imdulation, serve as the principal organs 

 of locomotion. 



Between the Testaceous Ehizopoda and CHiated Protozoa the alhance is even 

 less evident ; for in none of the latter do we meet "\;\ith shells like those of the 

 former, and in none is the relation between a lorica and its contents corre- 

 spondent to that of the shell and sarcode substance of Ehizopoda. It has 

 already been noted that the distinction between the two classes of Protozoa 

 founded on the silicious character of the shells or lorica) of the Ciliated, and 



