32 



INVERTEBRA TE ZOOLOG Y 



between ectoplasm and endoplasm. Typical members of this 

 group (Fig. 17) possess chromatophores, frequently brown or 

 yellow in the lower forms and green in the higher. Especially in 

 the latter, chlorophyll is found. While members of this subclass 

 are characteristically capable of manufacturing their own food, 

 there are but few which are entirely lacking in power of taking 

 in either fluid or solid foods. Contractile vacuoles are usually 

 present in the fresh-water forms either as a simple pulsating 

 vacuole or as a more highly complicated system of vacuoles and 

 reservoirs. Division is usually by longitudinal binary fission. 



Fig. 19. 



Figs. 17-19. — Typical examples of Phytomastigina. 17, Chromulina showing 

 chromatophores and a distinct shell {redrawn from Hofcndcr); IS, Chilomonas 

 Paramecium, a form without chloroplasts, common in laboratory cultures 

 (redrawn from Dofiein); 19, Peranema trichophorum, a species with a long 

 flagellum, only the tip of which vibrates {redrawn from Dofiein). 



In most cases the cell organs become duplicated before separa- 

 tion of the body begins. In some species of Euglena, "division 

 cysts" are formed, and in these instances reproduction does not 

 occur during motile stages but only after the flagellum has been 

 cast off and the individual has entered a quiescent phase. Many 

 of the members of this subclass have but a delicate pellicle or 

 lack it entirely and are thus capable of extreme changes in body 

 form as exemplified in the peristaltic or "euglenoid" movements 

 of the bodies of Euglena and some of its colorless allies, Astasia 



