132 



BIOLOGY OF THE PROTOZOA 



Chrysoflagellida and Chloroflagellida (Fig. 125, p. 258), or, as in the 

 Dinoflagellida, it is deposited in the form of definite plates, which 

 may be highly sculptured or drawn out into characteristic ridges, 

 ledges or spines (Fig. 68). 



A 



B 



Fig. 68. — Types of Peridinidse with cellulose shells composed of plates. A, 

 Goniodoma acuminatum Ehr.; B, Gomjaulax Kof. {F) transverse furrow with epitheca 

 above and hypotheca below. {A, after Schiitt; B, after Kofoid.) 



(6) Motile Organoids.— The organoids by which Protozoa move 

 are to be considered as modifications of the cortex, although some 

 t^'pes, as shown in the preceding chapter, are derived in part 

 from internal kinetic elements (flagella and some pseudopodia) . 

 Three main types are distinguishable— flagella, pseudopodia and 

 ciHa, each of which is sufficiently distinct from the others to furnish 

 a natural basis for chissification of the Protozoa, a basis of classi- 

 fication which Dujartlin first employed to create the three great 

 groups les flageUes, ks rhizopodes, and les cilies. Each type is sub- 

 ject to man\' variations, due to inherent differences in the motile 

 organoids themselves, or to fusion in various ways leading to struc- 

 tures of considerable complexit\'. 



It is extremely difficult to decide whether fiagella or pseudopodia 

 are the more primitive in type. From most general text-books on 

 Zoology we learn that the matter admits of no question, and are 

 taught that the pseud()i)odium is the most primitive form of motile 

 organ in the animal kingdom. This certainly has been the most 

 widely accepted view. Many a generalization referring to Protozoa, 

 however, which has found its way into general works on Biology, 

 appears to have been drawn from the conditions in some one organ- 

 ism which is conspicuous by reason of its abundance and ease of 

 study. It would sometimes appear, indeed, that the common 

 species of Parariiecium and Ainoeha proteus, to many general writers, 

 constitute the Protozoa. This seems to be the case with the problem 

 of pseudojjodia and fiagella, the argument being that a pseudopo- 



