FLA CELL A TA -PA NTOS TO MA TA ; FLA CELL A TA-EUS TO MA TA. 39 



Lembtis, Condylostoma, and Spirochona, among the Ciliate class of the 

 Protozoa. Furthermore, as recorded by the author in the systematic 

 portion of this treatise, the characteristic adoral fringe of certain higher 

 Ciliata, such as Stentor and Euplotes, is developed through the splitting 

 up of a similar primary undulating membrane. 



In the next cycle of advance, as exemplified in the order of the Rhizo- 

 Flagellata, the several genera, Mastigamceba, Rhizomonas, and Podostoma, 

 while retaining the general characteristics of repent or floating Amoeba, 

 have superadded a distinct flagellum, and undoubtedly constitute the root- 

 forms of several leading sections of the Protozoa hereafter referred to. 

 The retraction of the pseudopodic processes of the Rhizo-Flagellata, with 

 the retention of the flagellum and capacity to incept food at any point 

 of the periphery, is alone required to perfect the passage to the next 

 succeeding order, that of Flagellata-Pantostomata. In this group we find 

 a considerable diversity in the number and character of the flagellate 

 appendages, this organ being single in such simple types as Monas and 

 Bodo, double in Spumella and A nthophysa, while in others such as Tetramitus, 

 Hexamita, and Lophomonas, the number is very considerably increased. It 

 is among the Polymastigous section of this order, somewhere near Lopho- 

 monas, that the remarkable compound marine type Magosphtzra planula, 

 PI. I. Figs. 12-17, upon which Professor Haeckel has proposed to found a 

 new class group entitled the Catallacta, should apparently be placed. A 

 special feature of Magospkcera, as described by Haeckel, is exhibited by 

 its tendency to revert to a repent amoeboid phase pending the process 

 of encystment and reproduction. A similar disposition is, however, as 

 hereafter shown, shared by the majority of the Pantostomata. 



In proceeding to the next group or order in the direct line of evolu- 

 tion, the boundary line that circumscribes the class of the Pantostomata is 

 necessarily traversed, and the associated forms, while still characterized 

 by the possession of one or more flagellate appendages, exhibit their 

 higher grade of organization through the development of a well-defined 

 oral aperture. This order, upon which is here conferred the title of the 

 Flagellata-Eustomata, embraces among its more familiar genera the types 

 Euglena, Astasia, Noctiluca, and Anisonema. The interesting order of the 

 Cilio-Flagellata, including chiefly the Peridiniidae and a few aberrant 

 forms such as Heteromastix and Mallomonas, are alone wanting to make 

 the phylogenetic line from Amoeba to the most highly specialized class 

 of the Protozoa, that of the typical Ciliata, entirety complete. Arriving 

 at the termination of this evolutionary line or phylum, it is requisite 

 to make a passing reference only to the group of the Opalinidae, which, 

 although possessing no oral aperture, are plainly retrograde forms of 

 Holotrichous Ciliata, exhibiting, by reason of their endoparasitic habits, a. 

 similar loss of this otherwise essential organ of nutrition as obtains in 

 the corresponding parasitic Cestoidea among the Annelidous, or the 

 Rhizocephala among the Crustaceous sections of the Invertebrata. 



Returning once more to the Amcebina, and following out the line that 



