CILIOPHORA 107 



Epistylis. As Carchesium^ but the stalk is purely cuticular and non- 

 contractile. In fresh waters and marine. 



Order CHONOTRICHA 



Ciliata, permanently sessile by the posterior end upon the bodies of 

 Crustacea; with the peristome represented by a spiral funnel at the 

 anterior end, coiled clockwise, ciliated inside, and leading to the 

 mouth; and the rest of the body naked. 



A small but very interesting group which shares with the Prociliata 

 two characteristics not found elsewhere in the class, namely (i) that 

 their nuclei are of one kind only and at mitosis form two sets of 

 chromosomes (see p. 22), (2) that they form numerous gametes, 

 which unite in the same way as those of members of the other classes 

 of the phylum. In the Chonotricha the reproduction, both sexual and 

 asexual, is carried out by buds. The nucleus contains a large achro- 

 matic mass which acts as a division centre. 



Spirochona (Fig. 93). Shaped like a slender vase. On the gills of 

 GammaruSj etc., in fresh and marine waters. 



Subclass sue TORI A 



Ciliophora of which all but a few primitive forms lose their cilia in the 

 adult; and which possess one or more suctorial tentacles. 



A few members of the group are free ; a few are endoparasitic ; most 

 are attached, and these have usually a cuticular stalky which is often 

 expanded at the end to form a shallow cup in which the animal sits or 

 a deep one which encloses it. 



The suctorial tentacles contain a tube, lined by ectoplasm, which 

 opens at the end, where there is often a knob. In some species there 

 are also solid, sticky tentacles, used to capture prey. 



Reproduction by simple binary fission does not occur. In a few cases 

 fission is equal or almost so (Podophrya, Sphaerophrya^ Fig. 86 F'),but 

 here one of the products differs from the parent in losing its tentacles 

 and acquiring cilia and thus resembles the buds of other species. This 

 happens whether the parent be a stalked or a floating form. Most species 

 multiply by typical budding. The buds may be external (Fig. 95 B) or 

 formed in brood pouches (Fig. 94) from which they escape when they 

 are ripe. External budding is the more primitive, internal the com- 

 moner process. In either, one bud or more than one may be formed 

 at a time. The buds (Fig. 86 H), whether external or internal, are 

 usually ciliated and at first without tentacles ; the cilia form a girdle 

 round the body, with sometimes the vestige of an adoral wreath. 

 Certain species form also unciliate and often tentaculate offspring by 

 external budding. Some species will, in unfavourable circumstances, 



