102 MANUAL OF ZOOLOGY. 



DISTRIBUTION OF THE INFUSORIA IN SPACE AND IN TIME. 

 The Infusoria have at the present day an almost universal dis- 

 tribution, being found in all collections of fresh and salt water, 

 where decaying organic matter is present, and where the other 

 conditions of life are favourable. A few are parasites in the 

 interior of other animals (Opalina\ but the true affinities of 

 these are doubtful. Owing to the fact of their generally want- 

 ing any hard structures which could have been preserved in a 

 fossil condition, no true Infusoria* can be said with certainty 

 to have existed in former periods of the earth's history, though 

 they have doubtless abounded in past time as now. The only 

 possible exceptions to this statement are certain microscopic 

 bodies which occur in the Chalk-flints, and which Ehrenberg 

 considered to be the protective carapaces of Peridinium and 

 allied forms of flagellate Infusoria. 



LITERATURE. 



[In the subjoined list, as well as in those which will be subsequently 

 given, it is hardly necessary to say that nothing further will be attempted 

 than to furnish the student with a brief and limited selection from the nu- 

 merous works and memoirs relating to the animals belonging to each sub- 

 kingdom. It has also not appeared needful to cite the names of well- 

 known manuals and text-books of zoological science, save where these 

 contain special information.] 



GENERAL WORKS. 



I. 4< Die Klassen und Ordnungen des Thier-Reichs," vol. i. Amorphozoa. 



Bronn. 



' Manual of the Protozoa." Greene. 

 Micrographic Dictionary." Griffiths and Henfrey. 

 The Microscope and its Revelations." 5th ed., 1875. Carpenter. 



Life-Histories of Animals." Packard. 



Recent Researches among some of the more Simple Sarcode Organ- 



isms." 'Journ. Linn. Soc.,' vol. xiii., 1877. Allman. 



GREGARINIDA. 



7. "Icones Histiologicse," vol. i. p. 7. Kolliker. 



8. ' Ueber die Natur der Gregarinen." ' Miiller's 



Miiller's Archiv fur Anatomic,' 

 1848. Stein. 



9. "On a new Species of Gregarina to be called Gregarina gigantea" 

 'Quart. Journ. Microscop. Science/ vol. x., 1870. Van Beneden. 



MONERA. 



10. "Monographic der Moneren." Jenaische Zeitschrift fiir Medecin und 

 Naturwiss.,' vol. iv., 1868. (Translated in 'Quart. Journ. Micro- 

 scop. Science,' 1869.) Heeckel. 



1 1. " Beitrage zur Kenntniss der Moneren." Schultze's ' Archiv fiir Mik- 

 roscopische Anat.,' vol. i., 1865. Cienkowski. 



" Fossil Infusoria " are often spoken of as forming more or less exten- 

 sive deposits in the earth's crust, but the organisms so named are really 

 Diatoms and Polycystina. 



