NATURE OF THE CILIA, FLAGELLA, AND TENTACLES. 



The spaces occasionally seen in the endoplasm, and which transmit light more readily than 

 the rest, are called vacuoles; they may exist as spaces tilled with water, and usually they con- 

 tain, besides the water, a greater or less portion of the vegetable or animal matter which has been 

 introduced into the body as food. They must not be confounded with the contractile vesicle. 

 Besides these, there is the nucleus or endoplast, which is surrounded, in part, by the granular semi- 

 fluid endoplasm, and which is also in contact with the 

 deeper layers of the ectoplasm. Colouring matter, diffused 

 or localised, is seen in the endoplasm, and this inner pro- 

 toplasm produces the minute particles or spores which escape 

 and develop into new individuals. 



In all Infusoria, the cilia and their varieties, the flagella 

 and the tentacles are extensions of the substance of the 

 body. In the minute flagellate animalcules the flagellum, 

 which is an elongated whip-like cilium, is an extension of 

 the delicate ectoderm : in the Ciliata the cilia arise from 

 the special layer beneath the hyaline cuticle ; and the long 

 suckers of the Teiitaculate order are probably extensions of 

 the same tissue. The cilia differing in dimensions and 

 shape in some Infusoria are the minute hair or eyelash- 

 looking vibratile appendages which mainly move their posses- 

 sors, or produce currents in the water when the Iiifusoriaii F *S- 8. A, B, STYLONYCHIA MYTILUS, SHOWING 



! ml ,. , -.. .. CILIA. STYLES, AND UNCINI J C. EUROLEPTUS. 



is fixed. They appear to move actively in one direction, lAfUr stein ) 

 and to return to their original position by their elasticity. 



The tops move forwards and backwards, and it is noticed in certain species that the ciliary lashing is 

 consecutive in a series, and that it produces the appearance of rotation, as in the Rotifera (pp. 24.5-9). 

 They are semi-solid and elastic, and they are moved by the contraction of the endoplasm at their base. 

 The vibratile cilia are arranged in. bands only, in certain families, and universally in others. Some 

 Infusoria have some cilia which are elongate, flexible, but not movable, and they are then called 

 setfe ; and in one interesting genus (Halterici) these long hairs are utilised when the animal makes 

 its sudden jumps. Some Ciliate Infusoria have these setae stout, and placed on the ventral, or 

 uiider-surface of the body, or at the extreme ends, and then they are called styles. In some instances 

 the ends of the styles are branched or feathered. In a family of the Ciliata, the Oxytrichidfe (p. 371), 

 there are claw or sickle-shaped appendages, which are modified setae, called hooks, or uiicini, and some 

 of the species carry all these remarkable outer structures for the purposes of locomotion and pre- 

 hension (Fig. 8). The body is, in some Infusoria, furnished with fin-like, thin, vibratile membranous 

 fringes (Fig. 9), and in one important group of the Flagellata the collar of the animalcule, which 

 exactly resembles that of the cell of the sponge, has its protoplasm in streaming movement, which 

 carries the particles coming in contact with the outside over the top to the mouth within. The 

 tentacles of the Tentaculifera resemble the pseudopodia of Rhizopods more or less ; some have a disc- 

 shaped sucker at the top, and are hollow, being filled with semi-fluid eiidoplasm. A spiral fibre 

 is seen 011 the outside of some tentacles, and in one family there are no terminal suckers. 



Whilst some Infusoria take in food at any part of their body, the morsel simply sinking into the 

 soft protoplasm, and carrying with it a small quantity of water, forming thus a vacuole, in others it 



is carried in the direction of a particular orifice, slit, or tubular 

 cavity, by currents in the water produced by certain cilia. In 

 some species the mouth-opening is always visible, in others it is 

 small, and only visible at the time of the capture of prey, and in 

 a few it is so large that a morsel is often swallowed nearly as large 

 as the captor. The mouth, in the most perfect forms, consists of a 



passage in the ectoplasm structures, which can dilate, and the lining of which is plaited, folded, and 

 even furnished with a layer of rod-like teeth (Fig. 10). This part is often capable of protrusion, and 

 on opening it leads to the exposed semi-fluid endoplasm, and not to anything like an oesophagus and 

 stomach. The morsel simply sinks into the mass with a little water, and forms a vacuole. 



