SYSTEM A TIC SUR VE Y. Ill 



Modified flagellate torms are included in the groups Dinoflagellata 

 and Cystoflagellata, in both of which there are two flagella, differ- 

 ently placed in the two cases. In the first are included Peridinium and 

 Ceratium ; in the latter, the large phosphorescent Noctiluca. They 

 form an important part of the plankton of lakes and sea. 



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 

 parasitic. 



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

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



FIG. 52. Optical section of a Radiolarian (Acttnomma). 

 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. 



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 Ophryodeiidron, without suctorial tentacles. 

 Some, like Spfaerophrya t are minute and parasitic. 



D. Predominantly encysted Protozoa. Sporozoa. Forms 

 like Gregarina and Monocyslis are included in a group of the (n) 

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

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

 Coccidium 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 



