DISTRIBUTION. 



icy 



plete covering of cilia. These cilia are found in different genera and 

 species to exhibit three separate plans of distribution, which are further 

 remarkable as coinciding essentially with those three patterns of ciliary 

 distribution exhibited by the three Ciliate orders of the Holotricha, Peri- 

 tricha, and Hypotricha. Thus, the simple forms Urnula epistylidis, and 

 Acineta linguifcra, furnish examples of Holotrichous ciliated embryos ; 

 Podophrya fixa and P. cyclopinn, Peritrichous ; while in those of Deiidro- 

 covietes paradoxa, OpJiryodendron abietiiiuin, and Heniiophrya genimipm'a, 

 such ciliation essentially corresponds with that of the Hypotrichous series. 

 Paying due regard, therefore, to the morphologic axiom that the embryonic 

 history of the higher species foreshadows or epitomizes the adult state or 

 states of others lower in the organic scale, the deduction is unavoidably 

 arrived at that the Tentaculiferous group of animalcules represents a series 

 of organisms occupying a position morphologically higher than that of 

 any of the Ciliata, and all of the leading divisions of which latter are 

 passed through or structurally represented by the Tentaculifera during their 

 earlier or embryonic state. It is a further noteworthy fact that the em- 

 bryos presenting a Holotrichous pattern of ciliation are met with in asso- 

 ciation with the simplest representatives of the Acinetidae, while in the most 

 complex ones, such as HcmiopJirya and Ophryodendrun, it assumes the 

 Hypotrichous type. This last-named circumstance may be cited as further 

 correlative testimony towards the evidence already adduced in support of 

 the higher organization of the Hypotricha as compared with the Peritricha. 

 The innumerable intercalating relationships and affinities that serve to 

 bind together and unite in one harmonious whole the several orders of the 

 Ciliata, are discussed at length in connection with the preliminary defini- 

 tions given of each respective subdivision of the class. 



Taking the evidence now submitted in its complete form, and havino- 

 regard to the innumerable intricacies exhibited in the organization and 

 development of the class Tentaculifera, the position of the highest factor 

 in the Protozoic sub-kingdom is herewith accorded to it, and the antici- 

 pation at the same time submitted, that future investigation will serve to 

 establish on a still more substantial basis the affinities between this group 

 and the more elementary factors of the Hydrozoic series. 



Distribution of the Infusoria. 



Although, taken as a whole, and as already intimated in general terms 

 in the opening paragraph of this volume, the Infusoria exhibit practically no 

 limit to their distribution, it will be found on a closer examination that many 

 out of the various groups, families, and genera present a certain fixed order 

 of diffusion. Among these, some may exclusively inhabit salt water, and 

 others fresh, the several secondary conditions of both these latter elements, 

 whether fresh or stagnant, being also productive of special forms or types. 

 Water in its various conditions, as above indicated, by no means represents, 



