INFUSORIA. 45 



absorbed, the peristome border is now displayed, and the business of adult life com- 

 menced. Another sort of sub-division has been recorded by Stein, and confirmed by 

 others. The body divides into two unequal parts, after which the lesser one is set free, 

 and then enters into genetic union with some other normal Vbrticella. This union is 

 supposed to produce a rejuvenescence, which means a capacity to continue the pro- 

 cess of multiplication by self-division. That the union is followed as in the Flagellata, 

 by encystment and sporular sub-division, has not been demonstrated. Perhaps this 

 word of caution is necessary ; the individual Vbrticella may often be seen with the 

 posterior ciliary wreath. This is not always an indication of recent division, for 

 when these animals become dissatisfied with their surroundings they produce the 

 extra cilia, and remove from the old pedicle, and set up in a more congenial place. 



Among the forms allied to Vbrticella we may notice that in Spirochonia the attach- 

 ment is by means of a disc, and the peristome is developed into a hyaline, spirally con- 

 volute membranous funnel. Stylonichia is similar, except that the body is mounted 

 on a rigid pedicle ; in Mhabdostyla the body is like that of Vorticella, but the pedicle 

 is not contractile, but flexible. In Carchesium the zooids are united in social tree- 

 like clusters, but the muscle of the pedicle does not extend through the main trunk ; 

 the individuals can withdraw themselves to the point of branching of their stalk, but 

 the colony cannot withdraw itself from its position. In Zoothamnium, on the other 

 hand, the muscle is continuous throughout the colony. In this genus there are 

 zooids of more than one form and size in the same colony. In the genus JEpistylis the 

 branched pedicle is rigid throughout, the base of the body alone being contractile. 

 Members of this genus are, doutless, next to those of Vorticella, most frequently met 

 with. Their tree-like colonies are readily seen by a hand lens on aquatic plants. The 

 carapax and gill chambers of the cray-fish, and the shells of aquatic snails, are also rich 

 hunting grounds for these creatures. Opercularia differs from Epistylis in the fact 

 that the ciliary disc is attached to one side of the oral entrance, and is usually elevated 

 to a considerable distance above the margin of the peristome, like a lid. They are 

 often seen as commensals on aquatic larvae and Entomostraca. 



The loricated VaginicolinaB is not less rich in surprisingly beautiful forms. Vagini- 

 cola has the sheath erect, sessile, and open at the top. The animalcule is fastened to 

 its case, protruding its body and spreading its peristome ; at the least disturbance in its 

 surroundings it instantly retracts, soon to very cautiously again protrude its body. Those 

 species with a lid to close the case when the animal is withdrawn, have been placed in 

 the genus Thuricola. T. crystalina is a common species. If the case 

 is pedicellate and open, the form is a Cothurnia (Fig. 21) ; if, in addi- 

 tion, there is a corneous lid, it is a Pyxicola; if a fleshy lid, Pachy- 

 trocka. All these forms may be looked for on Entomostraca and aquatic 

 plants, like Lemna, Anacharis, and Myriophyllum. 



In Platycola and Lagenophrys the cases rest on one side. Fig. 45 

 represents the charming Platycola dilatata, the brown, laterally at- 

 tached case occurs on fresh-water plants. The animalcule is quite 

 similar to those of a majority of the loricate forms. There are two 

 ffenera, whose social individuals inhabit common gelatinous matrices, 



-, ^ , ■, ^ ■ h 1 ^ r\ FioM.— Platycola 



VIZ., Ophionella and Ophrydium. One species oi the latter genus, (J. dUatata, magni- 



„ ,.,,, „, -,1, ^ fied 300 times. 



versatile, may often be seen in shallow fresh and salt water as more or 



less spherical green masses, sometimes floating or resting on the bottom, and may easily 



be mistaken for algaB, such as Tetraspora or JVbstoc. These masses are inhabited by 



