694 



Tl'NICATA. 



the back: but the position of the ovary varies. 

 The mantle and its envelope, when exposed to the 

 sun, exhibits the colour of the rainbow, and are so 

 diaphanous, that the entire structure of the animal 

 can be seen through them. In many they ara fur- 

 nishetl with perforated tubercles. The animal has 

 been seen to come out from its envelope without 

 appearing to suffer pain. The most curious cir- 

 cumstance respecting these animals is, their re- 

 maining united for a long time, just as they were 

 in the ovary, and thus swimming in long chains, 

 where the individuals are disposed in different 

 ways, but euch species always according to the 

 same order. 



Many of the animals of this class, from their 

 thus being united in a common mass, have been by 

 several naturalists mistaken for compound animals, 

 like the polypi ; but they are widely different from 

 them and all the lower orders of the animal king- 

 dom. The aggregated Tunicated beings are inde- 

 pendent and individual animals, each of which is 

 provided with a mouth, and an aperture for the 

 ejection of digested matter, applicable to the in- 

 dividual wants, and unconnected with the general 

 nutrition of the common mass. 



It is quite certain that in some species little in- 

 dividuals have been observed adhering to the in- 

 terior or larger ones, by a peculiar kind of sucker, 

 which were different in form from those that con- 

 tained them. 



Lamarck divides this class into the two following 

 orders. 



I. ASCIDIARIA. Animals either isolated or in 

 groups, without internal communication, and not 

 forming essentially a common mass. 



II. BOTEYLLARIA. Agglomerated animals, al- 

 ways united, and constituting a mass with a com- 

 mon covering. 



ORDER I ASCIDIARIA. 



Animals disunited, living either in an isolated condition, or 

 C( nirregated in groups, wit limit any internal communication in 

 tneir organisation, and not forming a common mass. 



The mantle and its cartilaginous envelope, which is frequently 

 verv thick, resemble sacs every where closed, except at two 

 orifices, which correspond to the two tubes, of several bivalves, 

 one serving to admit water, and the other for the foces. The 

 bronchi.^ lorm a large sac, at the bottom of which are the mouth 

 and the visceral mass. The envelope is much larger than the 

 mouth, which is fibrous and vascular, and on which, between 

 the two tubes, is one of the ganglions. 1 hese animals attach 

 themselves to rocks and other bodies, and are destitute of all 

 power of locomotion; the chief sign of vitality which they ex- 

 hibit, consists in the absorption and evacuation of water through 

 one of their orifices : when disturbed, they eject it to a consi- 

 derable distance. 7 hey abound in every sea. 



Miimmaria. Body free, naked, oval, or sub-globular, termi- 

 nated at the summit by a single opening ; destitute of tenta- 

 cula at the orifice. 



Kiapillaria. Body free, naked, sub-globular, terminated 

 posteriorly by a kind of peduncle, with two conical perforated 

 and tentacular papillre at its superior extremity ; each of the 

 orifices provided with three setaceous tentacula. 



jltcidia. Body oval, conical, or cylindrical, sometimes club- 

 shaped, containing, in its exterior envelope, more or less coria- 

 ceous or sub-gelatinous matter, fixed by a widened or peduncu- 

 lated base, and terminated above by two short, indistinct, une- 

 qual siphons, the orifices of which are provided with radiated 

 cuntitcula. 



This genus consists of three sec- 

 tious, viz. 



1. Body sciated, short, or slight- 

 ly elongated. 



2. Body sessile, and considera- 

 bly elongated. 



3. Body pedunculated, or nar- 

 rowed into a peduncle beneath. 



Atcidia intettinalii. The Intes- 

 tinal Asridia. Body elongate,!, 

 smooth, flaccid ; orifices approxi- 

 mated at the apex. Inhabits the. 

 teas i.f Europe. 



W/Mi. Body freo, oblong, cylindrical, truncated at both enSt. 

 or at one only ; orifices terminal, or not .so. one ulways longer 

 tliini tin- other, and transverse, with a movable opercoliun, mid 

 the other tubular; exterior envelope sott or sub-cartilaginous, 

 provided with hollow tubercles, which act as suckers, variable 

 in number and disposition. 



This genus consists of two Sections, viz. 



1. Those with the body truncated. 



2. Pointed at one or both extremities. 



ORDER II BoTttYLLARIA. 



Agglomerated animals, always united, mid coiMitnthn: a 

 common mass by their re-union, as they appear to communi- 

 cate organically with one another, ami in this reflect seem til 

 In- a roi meet ill!.' link between the ]\l oil u-ca anil /oopbvte-. In- 

 ilepeinli-iitly. hou ever, of their pen-liar organisation, these ani- 

 mals at first live and swim separately, ami only become united 

 at a certain snb-c<mi-iit period, a fact \\Iiich is in direct opposi- 

 tion to this opinion. 



The bronchi i- nf this Order, as In the Ascidi;e, form a large 

 sac. traversed by the alimentary canal before it arrives at the, 



mouth; their principal gUottoO is also situate hetwi the 



mouth mid the arms ; a nearly similar ili-po-it 'on obtains w itli 

 respect to the viscera and ovary ; not withstanding of which, 

 some of them have an opening at each extremity. 



Lamarck sub-divides the Order as follows : 



1. Animals floating in a common maw in water. 



2. Animals fixed upon marine bodies. 



SUB-DIVISION I. FLOATING ANIMALS. 



Pjtrosoma. Animals biferous. aggregated, forming by their 

 union a free, floating, cylindrical, gelatinous, hollow nu 

 ed at one extremity, and open at the other, and covered exte- 

 riorly with tubercles; orifices of the mouth exterior; anal 

 opening situate in the internal wall of the cavity of the rna ; 

 provided with two gemmiferous, opposite, and lateral sacs. This 

 mass swims in the ocean by the alternate contractions and di- 

 latations of the individual animals which compose it. 



These animals terminate in a point on the exterior, so that 

 the whole external surface of the tube is bristled with them ; 

 the bronchial orifices are pierced near tlieir points, and the anal 

 opening debouches in the internal cavity of the cylinder. A 

 Pyrosoma may consequently be compared to a great number of 

 stars of Botrylli strung together, the whole of which is move- 

 able. They exhibit a phosphorescent light during night, and 

 are found in the Mediterranean. 



SUB-DIVISION II.-ADHERENT ANIMALS. 



1 . Animals forming distinct groups, each disposed around a 

 central cavity. 



hotryllu*. Aggregated biferous animals, adnate at the sur- 

 face of a thin, gelatinous, transparent crust, and composed of 

 numerous orbicular star-shaped systems, each system disposed 

 in a radiated form round a central opening. The bronchial ori- 

 fices are at the external extremities of these rays. Individual 

 animals ovoid, contracted below, thickest and rounded at the 

 summit, and perforated above towards each extremity ; mouth 

 situate near the circumference of the cyst, provided with eight 

 tentacula, of which four are larger than the others ; anal open- 

 ing near the centre ; furnished with two gemmiferous sacs. 



If an orifice be irregular, a single animal only contracts; and 

 if the centre be touched, they all contract. 



1'olycyclus. Animals biferous, congregated, and united in a 

 common mass ; gelatinous, thick, convex, adherent, the surface 

 studded with many-mouthed orbs, each having a cavity in !), 

 centre ; ten or twelve separate openings disposed in a circle 

 around the cavity, with interior siphons communicating be- 

 tween these and {he central aperture. 



I'olychnum. Animals aggregated, biferons, sunk in a gela- 

 tinous mass, depressed, and rough with small papilla?; most of 

 them forming stelliform systems, and disposed in a radiated 

 form round a central opening ; mouth provided with six ten- 

 tacula ; anal opening not apparent externally ; one gemmife- 

 rous sac hanging under the animal, with a filamentary termi- 

 nation. 



2. Animals disposed in concentric circles, forming the com- 

 mon mass. 



Diagotna. Animals aggregated, biferous, congregated, and 

 by their union forming a common body, fixed, semi-gelatinous, 

 orbicular, multicellular, with projecting compressed cells, each 

 furnished with two orifices, and disposed in many concentric 

 circles ; mouth furnished with six lanceolate tentacula. 



No particular si/item* fanned by the disposition of the ani- 

 mals in the cominnn mcui. 



1 . Provided with two orifices for each animal, which appear 

 to be external. 



Diitomiu. Animals biferous, separate, associated in a sub- 

 coriaceous mass, extended in a crust, and covered with scat- 

 tered warts, and margined with six teeth. 



SigiUina. Animals biferous, forming by their union a com- 

 mon gelatinous body, conically elongated, sub-pediculated, with 

 scattered tubercles ; animals not disposed in particular or dis- 

 tinct systems ; tubercles of the surface with two pores ; mouth 

 furnished with six tentacula. and six teeth at the anal opening. 



2. One orifice only, externally apparent, for each animal. 

 Synoirum. Aggregated animals, living in cylindrical fle-hy 



projections, obtuse at the summit, and originating in a fixed 



