CLASSES OF PROTOZOA 1 35 



As (9) Ciliata are included a very large number of forms, more or 

 less closely resembling Paramcecium or Vorticella, and very abundant 

 in infusions ; some, such as Opalina, in the intestine of the frog, are 

 more or less parasitic. 



As specially modified Ciliata are included (10) Acinetaria, highly 

 specialised forms, ciliated when young, but usually fmrnished when adult 

 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 Sphcerophrya, are minute and parasitic. 



D. Predominantly encysted Protozoa. — Sporozoa. — Forms 

 like Gregarina and Monocystis are included in a group of the (11) 



Fig. 63. — Optical section of a Radiolarian (Actinomnia). 



—After Haeckel. 



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

 'nucleus; c', middle shell within central capsule; c2, outer shell 

 in extra-capsuleir substance. Four radial spicules hold the 

 three spherical shells together. 



Sporozoa, the Gregarinida in the strict sense. They are parasites in 

 the gut or body cavity of many Invertebrates, especially Arthropods. 

 Coccidiiun is a type of the Coccidiidea, which are intracellular parasites 

 occurring in Arthropods, Molluscs, and Vertebrates. A very im- 

 portant group, with a life-cycle essentially similar to that of the 

 Coccidiidea, are the Haemosporidia, which are parasitic in the red 

 blood corpuscles of Vertebrates. The malaria parasites belong to this 

 group. In many of the Haemosporidia a part of the hfe-cycle takes 

 place in an intermediate host, usually a mosquito or a tick. 



Other groups of the Sporozoa are the Myxosporidia, with peculiar 

 nematocyst-hke organs (Invertebrates and cold-blooded Vertebrates), 

 and the Sarcosporidia, which are found inside the striped muscles of 

 warm-blooded Vertebrates. 



