90 THE ANATOMY OF IXYERTEBRATED ANIMALS. 



which the food is forced, and, passing into the endosarc, re- 

 mains for some time surrounded by a globule of contempo- 

 raneously ingested water — a so-called " food-vacuole." Prof. 

 H. James Clark, who has recently carefully studied the Fla- 

 gellata, points out that, in Bicoswca and Codonoeca, a fixed 

 monadiform body is inclosed within a structureless and trans- 

 parent calyx. In Codosiga a similar transparent substance 

 rises up round the base of the flagellum, like a collar. In 

 Saljnngoeca the collar around the base of the flagellum is 

 combined with a calycine investment for the whole animal. 

 In Anthophysa, there are two motor organs — the one a stout 

 and comparatively stiff flagellum, w T hich moves by occasional 

 jerks, and the other a very delicate cilium, which is in con- 

 stant vibratory motion. 



The discrepancy between the two kinds of locomotive 

 organs attains its maximum in Anisonema, which presents 

 interesting- points of resemblance to Noctiluca. 



Multiplication by longitudinal fission was observed in 

 Codosiga and Antho})hysa, and probably occurs in the other 

 genera. In Codosiga the flagellum is retracted before fission 

 takes place, but the body does not become encysted ; in An- 

 thophysa the body assumes a spheroidal form, and is sur- 

 rounded by a structureless cyst, before division occurs. 



Conjugation has not been directly observed among most 

 of the Infusoria flagellata, nor do any of them exhibit a 

 structure analogous to the endoplastule of the Ciliata. 



Messrs. Dallinger and Drysdale have recently worked out 

 the life-history of several flagellate " Monads," which occur 

 in putrefying infusions of fish. They show that these Jtla- 

 gellata not only present various modes of agamic multiplica- 

 tion by fission, preceded or not by encystment, but that they 

 conjugate, and that the compound body which results (the 

 equivalent of the zygospore in plants) becomes encysted. 

 Sooner or later, the contents of the cyst become divided 

 either into comparatively large or excessively minute bod- 

 ies, which enlarge and gradually take on the form of the 

 parent. 



The careful investigations of these authors lead them to 

 conclude that, while the adult forms are destroyed at from 

 61°-80° C, the excessively minute sporules which have been 

 mentioned, and which may have a diameter of less than 

 a o (H) o o °f an mcn ? ma y be heated to 148° C. without the 

 destruction of their vitality. 



In JEuglena viridis (which, however, may be a plant), 



