440 THE PELON^A. 



THE simple or solitary tunicates are classed together under the name of Ascidiadae. 

 The common SEA-SQUIRT, figured on the left hand of the illustration, is a good example 

 of the typical genus. 



This animal, in common with all its kin, feeds mostly, if not wholly, upon the minute 

 vegetable organisms, such as the desmids, diatoms, etc., which abound throughout the 

 water, and the manner in which these substances are brought to the digestive organs 

 is equally simple and beautiful. "The mouth," writes Mr. Rymer Jones, "is quite 

 destitute of lips or other extensile parts, and situated, not at the exterior of the body, 

 but at the very bottom of a capacious bag inclosed in the interior of the creature. 



It is obvious, then, that whatever materials are used as aliment, must be brought into 

 the body with the water required for respiration ; but even when thus introduced, the 

 process by which they are conveyed to the mouth still requires explanation. 



A truly miraculous apparatus is provided for this purpose. The whole surface of the 

 respiratory chamber is covered over with multitudes of vibratile and closely set cilia, 

 arranged in millions, which by their united action cause currents in the water, all of 

 which flow in continuous streams directly towards the mouth. It is sometimes possible, 

 in very young and transparent specimens, by the aid of a good microscope, to witness 

 the magnificent scene afforded by these cilia when in vigorous action. 



' salientia viscera possis 



Et perlucentes numerare in pectore flbras.' 



The effect upon the eye is that of delicately toothed oval wheels revolving continually 

 from left to right, but the cilia themselves are very much closer than the apparent 

 teeth, the illusion being caused by a fanning motion transmitted along the ciliary lines, 

 producing the appearance of waves, each wave representing a tooth of the supposed 

 wheel. 



Whatever little substance, alive or inanimate, the entering water brings into the 

 branchial sac, if not rejected as unsuitable, lodges somewhere on the respiratory sur- 

 face, along which each particle travels horizontally, with a steady, slow course, to the 

 front of the cavity, where it reaches a downward stream of similar materials, which 

 hurries onward, receiving accessories from both sides, until at last the whole is brought 

 into the gaping mouth." 



Some of the Ascidia are beautifully colored with, orange, crimson, and white, though 

 others are plain and almost repulsive when dredged from the sea-bed. Several species 

 attain to a considerable size, being five or six inches in length. They do not seem to 

 like deep waters, being mostly found near low water-mark, and seldom at a greater 

 depth than nineteen or twenty fathoms. 



AT the right hand of the illustration is seen another British tunicate. This is the 

 CYNTHIA, one of a rather numerous genus, not uncommon on our coasts. The AGGRE- 

 GATED CYNTHIA (Cynthia aggregate?) is to be found on almost any substance that has 

 remained for any length of time below low-water mark, and stones, rocks, wooden piles, 

 or even the larger seaweeds, are frequently covered with these curious creatures, some- 

 times set in solitary state, and sometimes gathered together in groups by means of the 

 interlacing of the fibres by which they attach themselves. Some species are eaten, 

 Cynthia mierocosmus being the most in favor, and regularly brought to market for sale. 

 This animal derives its specific title from the multitude of animal and vegetable para- 

 sites that grow upon it, and so transform it into a little world. 



THE animal which is represented at the upper part of the engraving is the PELON^EA, 

 so called from two Greek words, the former signifying mud, and the latter to inhabit. 

 This animal, as its name imports, is in the habit of burying itself in the mud, where it 

 remains fixed and nearly motionless, respiring and obtaining nutrition by means of the 

 two open tubes seen at the smaller end. Only two, or perhaps three, species of this 

 genus are known, and the animal is found in northern Scotland and Norway. 



