1873.] the Invertebrata in relation to Evolution. 219 



investing substance, or directly through the pores, foramina, or fenestra- 

 tions of the calcareous or siliceous capsules protecting the contained 

 sarcode-bodies. In other instances, on the contrary, solid food is actually 

 consumed by mouthless beings, which simply open their bodies to receive 

 it; and this opening of the body may take place at any part of the 

 surface most convenient, or it may be restricted to a definite locality, 

 shadowing forth the permanent mouth of the Stomatoda, or even that of 

 the most primitive form of Hydrozoa. 



The annexed Table of arrangement is drawn up in accordance with the 

 foregoing remarks. 



Physiological Classification of the Protozoa. 

 Habit of life and mode of nutrition : — 



I. Parasitic . Gregarinida. 



II. Non-parasitic. 



A. Assuming food in a state of solution by absorption of the 



general surface. 



1. Indirectly through a medium 



a. Forming a cell-like envelope ThalassicollidcB. 



b. Lining porous canals in the common mass Tori f era. 



2. Directly through 



a. The pores or foramina of a calcareous shell Foraminifera. 



b. Fenestrations of a siliceous shell Tolycyatina. 



c. A more largely exposed surface Acant hornet rides. 



B. Assuming solid food by an adventitious mouth. 



1. At any part of the surface where the contact is made . . . Monera, Amoeba, $~c. 



2. At a definite part, determined by the opening of the shell Gromia,Diffli'gia,^c. 

 C. Assuming solid food by a permanent mouth. 



1. The same orifice being also excretory Infusoria. 



2. Discharging excreta by a rudimentary anus : Xoctilucida?. 



This Table may be said to afford us good general grounds for forming 

 an estimate of the relative superiority of the several types thus physio- 

 logically defined, and it is mainly in keeping with their more commonly 

 received distribution founded on structural particulars. 



A show of progressive improvement is seen in the respective sections 

 A, B, and C, though to all appearance the simplest group of animals in 

 existence, namely the Monera of Hackel, is included in the section B. 

 These rudimentary creatures are destitute of both nucleus and contractile 

 vesicle, though exhibiting activities in movement, taking food, and repro- 

 ducing their kind, not even second to those of Amoeba audits allies. The 

 smallest ciliated molecule endowed with animal life could not present a 

 more simple structure than that of the perfectly homogeneous and jelly- 

 like Monera. Indeed the evolution of any of the other primitive forms 

 from a plastic source like this is quite conceivable, though of course we 

 have no actual means of observing such a transmutation. 



Moreover the development of amceboids in some part of the life- 

 history of most Protozoa would appear to stamp that form as the 



t 2 



