REPRODUCTION OF THE INFUSORIA. 



363 



Vorticellidsfi. In the Stentors and some other genera the fission is oblique. The endoplast divides 



in every instance, and part remains with each individual, and the other organs, such as the mouth, 



anus, and contractile vesicle, are developed where they are wanting. 



Some Infusoria increase by a process resembling budding, and in this process, the important 



endoplast contributes a little process which accompanies the protrusion of the body membrane to form 



the bud. In Noctiluca (p. 374) the protoplasm beneath the cuticle becomes broken up into nodular 



fragments, which are protruded upon the external surface, and are finally liberated as very minute 



bodies resembling monads, and these grow into adult Noctilucse. 



In some instances the young grow within the body of the parent, but only at the expense of the 



endoplast. Portions of this separate and become embryos, which escape with their cilia, and either 



resemble the parent or grow into its shape as in the Tentaculifera. 



Another method of reproduction is when the Infusoria become quiescent ; a delicate covering 



is then formed over the body, and the quiet and encysted creatures have their internal tissue broken 



up into myriads of minute particles, which escape, and 



finally assume the shape and destiny of the parent. It 

 is found that sometimes an intermediate amcebiform con- 

 dition occurs (Fig. 14). 



Infusoria also reproduce after a process which some- 

 what resembles the conjugation in Algse amongst plants. 

 Swimming, or fixed by a common stalk, two animalcules 

 come in contact by their oral surfaces, and remain united 

 for a limited period. They swim about, and exist as one, 

 and in the Flagellata the flagella are withdrawn, and 

 amoabiform processes are cast forth. In other instances 

 the junction of different individuals, one often larger 

 than the other, persists. Under both circumstances the 

 reproductive energy of the couple is intensified. How, 

 is a matter of debate, but late microscopical researches 



by Butschli and Englemann show that during the process the original endoplast in both 

 animalcules breaks up into a number of fragmentary portions, and becomes lost among the 

 endoplasm. By-and-by a new endoplast is constructed through the gradual assemblage and 

 union with each other of fragmentary particles, and the new endoplast is common to both of 

 the animalcules when the conjugation is complete and lasting, as in Yorticella (Fig. 11); 

 while two or more, according to the normal number, are reproduced where the conjugation is 

 transient as in Paramecium (Fig. 2). Biitschli denies that embryos ai % e subsequently developed from 

 the endoplasts, and he considers that the conjugation is a mere vital stimulant to the decaying 

 energies of the animalcule. Before passing on to a short classification of the Infusoria, it is necessary 

 to mention that they have a most extraordinary distribution. Some families inhabit salt water, 

 others fresh ; some species live in running water, others in stagnant pools. Many species are parasitic 

 on, and others within, other Infusoria, and many groups of Iiivertebrata and Vertebrata. Many 

 are only found in animal, others in vegetable, infusions. One group is mouthless and essentially 

 endoparasitic. The Opalinidae inhabit the alimentary canals of insects, frogs, toads, and the 

 aquatic Annelida. Some Ciliata inhabit the stomachs of ruminants, some live in the human gut. 

 Others live fixed to fish, or crawl about the Hydra. The Flagellata are found in fresh and salt 

 water, and are often parasitic, and some inhabit human urine. In searching for ordinary and 

 well-known forms, the surface of pure and coloured fresh waters, and the leaves of the plants, should 

 be examined, and the waters of bogs and the sea-shore yield many new forms. The artificial 

 production of Infusoria, by infusing hay, meat, &c., depends on the existence of the germs in the 

 air, in the water, and collected about the plants. 



ORDER TENTACULIFERA (Huxley}. 



An example of this order has been noticed already, and it explains the characters of the group. 

 They are animalcules inhabiting either salt or fresh water, and many are parasitic on and within other 



Fig. 14. ICHTHYOPHTHIRR'S MULTIFILII8. 



(After Fouquet.) 



A, Adult ; B-O, different stages of development (.E, escape of 

 young); H, oral apparatus. 



