12 INTRODUCTION TO CLASSIFICATION. 



itself by means of its pseudopodia, which attach themselves to 

 nutritive particles, and then draw them into the substance of 

 the body. There is neither ingestive nor egestive aperture, 

 neither special motor nor prehensile organs, but the pseudopodia 

 perform each function as it may be required. 



But here, again, we labour under an imperfection of know- 

 ledge. For, although it is quite certain that the Rhizopoda 

 may multiply by division of their substance in a way somewhat 

 analogous to that which I detailed when speaking of the Grega- 

 rinida yet, as in that case, we have no knowledge of any true 

 sexual process. It is a most remarkable circumstance that 

 though these animals are abundant, and are constantly under 

 observation, we are still in doubt upon that essential point, still 

 uncertain whether there may not be some phase in the cycle of 

 vital phenomena of the ETiizopoda with which we are un- 

 acquainted ; and, under these circumstances, a perfect definition 

 of the class cannot even be attempted. 



Fig. 3. 



Fig. 3. Sphcerozoum ovodimare (after Haeckel), one of the complex Radiolaria. 



III. THE RADIOLARIA. 

 The simple forms of this group consist of microscopic masses 



