loS PHYLUM PROTOZOA- -THE SIMPLEST ANIMALS. 



with suctorial tentacles. They are fixed in adult life, and feed on other 

 Protozoa. As examples may be given Acineta ; Dendrosoma, forming 

 branched colonies ; and Ophryodendron, without suctorial tentacles. 

 Some, like Sphczrophrya, are minute and parasitic. 



D. Predominantly encysted Protozoa. Sporozoa. Forms 

 like Gregarina and Monocystis are included as (13) Sporozoa or 



FIG. 50. Optical section of a Racliolarian (Actitioiuma). 



After Haeckel. 



a., Nucleus ; b. , wall of central capsule ; c., siliceous shell within 

 nucleus; c' 1 ., middle shell within central capsule; c 2 ., outer shell 

 in extra-capsular substance. Four radial spicules hold the 

 three spherical shells together. 



Gregarinida. The others mostly resemble these types, but some, like 

 Coccidiuni, are permanent cell parasites. Gregarines are parasitic in 

 many different kinds of animals, including vertebrates. The Myxo- 

 sporidia peculiarly abundant in Fishes ; the Coccidia found in most 

 animals ; the Sarcosporidia inside muscle fibres, especially of Mammals ; 

 the Hremosporidia inside red blood corpuscles, are all classed as 

 Sporozoa. 



GENERAL NOTES ON THE FUNCTIONS OF PROTOZOA. 



Movement. --The simplest form of movement is that 

 termed amoeboid, as illustrated by an Amceba. In ordinary 

 conditions it is continually changing its shape, putting forth 

 blunt lobes and drawing others in. With this is usually 

 associated a streaming movement of the granules. A more 

 defined contraction, like that of a muscle cell, is illustrated 



