270 MANUAL OF ZOOLOGY. 



DIVISIONS OF THE TUNICATA. By Professor Huxley the 

 following arrangement of the Tunicaries is adopted : 



CLASS TUNICATA. 

 Order I. Ascldia Branchialia. 



Branchial sac occupying the whole, or nearly the whole, length of 

 the body ; intestine lying on one side of it. (AscitKada, Botryllus^ &>c.) 

 Order II. Ascidia Abdominalia. 



Alimentary canal completely behind the branchial sac, which is 

 comparatively small. (Clavellina, Doliolum, &*<:.) 

 Order III. Ascidia Larvalia. 



Permanent larval form. (Appendicularia.} 



The following subdivisions are those adopted by Mr Wood- 

 ward : 



CLASS TUNICATA. 



Fam. I. Asddiadtz (Simple Ascidians). 



Animal simple, fixed, solitary, or gregarious ; oviparous ; sexes 

 united ; branchial sac simple ; or disposed in (8 18) deep and regular 

 folds. 

 Fam. II. Clavellinida (Social Ascidians). 



Animal compound, fixed ; individuals connected by creeping tubular 

 prolongations of the common tunic through which the blood circulates 

 (or by a common gelatinous base). Reproduction effected by ova, or 

 by gemmation from the common tube ; the new individuals remaining 

 attached to the parent, or becoming completely free. 

 Fam. III. Botryllida (Compound Ascidians). 



Animals compound, fixed, their tests fused, forming a common mass 

 in which they are imbedded in one or more groups. Individuals not 

 connected by any internal union ; oviparous and gemmiparous. 

 Fam. IV. Pyrosomida. 



Animal compound, free and oceanic. 

 Fam. V. Salpida. 



Animals free and oceanic ; alternately solitary and aggregated. 



CHAPTER XLIV. 

 BRACHIOPODA. 



CLASS III. BRACHIOPODA (Palliobranchiata). The members 

 of this class are defined by the possession of a body protected 

 by a bivalve shell, which is lined by an expansion of the in- 

 tegument, or " mantle." The mouth is furnished with two long 

 cirriferous arms. The nervous system consists of a single 

 ganglion, placed in the re-entering angle between the gullet 

 and the rectum, so that the intestine has a " neural flexure." 

 The Brachiopoda are essentially very similar in structure to 



