28 THE E0T1FEEA. 



Eotiferon has six hollow limbs continuous, in true Arthropodous fashion, with the body- 

 cavity, and worked by opposing muscles passing down them, and is thus plainly linked to 

 the Crustacea and Insecta. Pedalion, in fact, is a Nauplius larva, and is yet a Eotiferon. 

 Order IV., then, is sufficiently separated from the rest by its Arthropodous limbs, 

 and by the use made of them ; and of the other three orders, it has been shown 

 above that, if we disregard some points of only two genera, we may say of orders I. II. 

 III. that they differ inter sc in their habits, and in the structure of their feet, tropin, 

 and ciliary wreaths. 



This seems a satisfactory first step towards classification ; but it is only fair to the 

 reader to warn him that it has been gained by omitting some parasitic Eotifera, as well as 

 a few very troublesome forms, such as Trochosphara, Apsilus, Microcodon, &c. 



I have dwelt on the differences in structure, as well as in habits, between the four 

 orders, in order to show that these four groups are natural ; but I do not propose to 

 use as ordinal characteristics any others than the mode of locomotion and the structure 

 of the foot ; and for this reason, that each of the first three orders has more than one 

 form of the tropin, or of the ciliary wreath, or of both. 



The Bhizota, for instance, have two forms of the tropin, and two of the ciliary wreath. 

 The Bdelloida have two forms of wreath, and the Plo'ima have many different forms of 

 both wreath and trophi. 



Before I proceed to divide these four orders into families, I must, however, digress 

 a little to explain and name the various types of trophi, as the classification partly depends 

 upon them. 



Mr. Gosse's treatise on " The Manducatory Organs in the Class Eotifera" essays to 

 show that these organs present seven principal types of structure, distinguished from 

 each other by the prominence of some particular part. 



To make this clear, it may be as well to re-state that, in the mastax of a Brachionus, 

 there are two hammer-like bodies or mallei (fig. 29, ms), which work on a kind of split 



anvil or incus (fig. 29, is), and that each malleus consists 

 of an upper part, the head or uncus (fig. 29, us), and of 

 a lower part or handle, the manubrium (fig. 29, mm) ; 

 while the incus consists also of two parts, the upper 

 divided into two symmetrical halves, the rami (fig. 29, 

 rs), which are supported on the lower piece or fulcrum 

 (fig. 29, fm). 



Now, in Brachionus all the trophi are well developed, 



but the other typical manducatory organs may be arranged 



in a series in which the mallei are successively degraded, 



Fig. 29.-Ma.iieate. while continually greater prominence is given to the incus ; 



at least in all but three types ; and in two of these the 



rami and unci are the prominent parts, while the third is distinguished by the close 



connection of the mallei and the rami. 



The typical trophi may, then, be named as follows : 



1. Malleate (fig. 29). 

 Mallei stout; manubria and unci of nearly equal length ; unci 5- to 7-toothed ; fulcrum 

 short ; as in Brachionus urceolaris. 



2. Sub-malleate (fig. 30). 

 Mallei slender ; manubria about twice as long as the unci ; unci 3- to 5-toothed ; 

 as in Euchlanis deflcxa. 



3. Forcijiate 1 (fig. 31). 

 Mallei rod-like ; manubria and fulcrum long ; unci pointed or evanescent ; rami much 

 developed and used as a forceps; as in Diglcna forcipata. 



1 In Furcularia, and in a few other genera, the rami as well as the mallei are rod-like ; and the 



