Organisms Consisting of One Cell S3/) 



such as an air bubble, or advance by springs, whicli recall 

 those of a hunting spider." - The rapid movement ahead, 

 running against obstacles, backing off, changing directions, 

 and turning around, remind one of the performances of an 

 ant under similar surroundings. Jennings' statement that 

 they are "usually found running about on the bottom, or 

 on the surface of objects in the water," ^ is no more a figure 

 of speech than would be a similar remark about a rabbit.* 



FIGURE 5. STYLONYCIIIA MYTILUS (aI'TER PUTmi). 



With reference to their food habits, Maupas's characteriza- 

 tion of them as "hunter ciliates," is truly descriptive. 



By contrast tlie movements of Stenostoma are slow and 

 simple indeed. In it locomotion is accomplished almost en- 

 tirely by surface cilia, and the well-nigh complete absence 

 of differentiation among these, as contrasted with the high 

 degree of differentiation and specialization of the cilia of 

 Stylonychia, may be taken as a reliable index to the dif- 

 ference in locomotor activities of the two creatures. 



(6) Comparison of a Radiolarian and a Jelly-fish 



Carrying the comparison of unicellular, "simple" or "un- 

 true" animals, with multicellular, "complex," "true," ani- 

 mals still farther, we will take up a Radiolarian for brief 

 consideration. Non-technical readers arc particularly urged 

 to look through the volume of 140 (juarto ])lates which il- 

 lustrate Haeckel's great Challenger Report on tiiis grouj). 



* Jennings copies this (liagram from Piitter sliowinp; a Sififloni/rhia 

 "creeping along the surfMce," which shows well the "helly" and the 

 "back" sides of the creature and the way in wliich it uses its cilia as legs. 



