FLAGELLATA. 193 



the more recent work of Biitschli, who has shown that the repro- 

 duction of these animals is essentially similar to that of the cell. 



The outer boundary of the body is usually formed by a cuticle, a 

 delicate, transparent membrane, the surface of which is beset with 

 vibratile and moving appendages of various kinds arranged in regular 

 order. In the smallest Infusoria, the Flagellate, we find only one 

 or two long whip-like cilia ; while the more highly differentiated 

 Ciliata are usually richly provided with cilia. According to the 

 varying thickness of the external membrane, which cannot in all 

 cases be isolated, and according to the different condition of the 

 peripheral parenchyma of the body, we get forms which change 

 their shape, forms which have a fixed shape and armoured forms. 

 If the simply organized Flagellata, which present numerous 

 affinities and transitional forms to the Alga3 and Fungi, are not 

 entirely removed from the region of the Infusoria, the two principal 

 groups to be distinguished are the Ciliata and Flagellata. 



Order 1. FLAGELLATA.* 



Infusoria of small size, characterised by possessing one or more long 

 whip-like cilia, usually placed at one end of the oval body. A row of 

 cilia sometimes and a nucleus always present. 



The Flagellata are Infusoria the locomotive organs of which 

 consist of one or more whip-like cilia, rarely with an accessory row 

 of cilia. They pass through an inactive stage, and in their develop- 

 ment as well as in their mode of nourishment are allied to certain 

 Fungi. 



The reasons for regarding the Flagellata as Protozoa are the perfect 

 contractility of the body, which is not surpassed by Myxomycetes 

 in the mastigopod stage ; also the contractility of the cilia, the 

 apparently purposed and voluntary movements, the occurrence of 

 contmctile vacuoles, and, as has been established in many cases, the 

 reception of solid substances into the body through an opening 

 at the base of the flagellum. Nevertheless these phenomena are by 

 no means a test of animal organization. 



The Monadince are a large group of Flagellata, found for the 

 most part in putrefying infusions, and are hard to distinguish from 

 the monads usually regarded as fungi. They reproduce themselves by 



* Besides Ehrenberg, Claparede, and Lachmann, loc. cit., compare Stein, 

 "Organismus der Infusionsthiere," Tom. III., 1878. Biitschli, " Beitrage zur 

 Kenntniss der Flagellaten," Zeitsclir. fur Tf 'iss. ZooL, Tom. XXX. Dallinger 

 and Drysdale, "Researches on the Life-history of the Monads," Monthly 

 Mieroscop. Journal, Tom. X. XIII. 



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