xxvi GENERAL INDEX. 



CHAPTER XIX. 



TUNICATA. 



Page 



TUNICATA General survey of the class 479 



Anatomy of Phallusia nigra . . ....', , : . . 479 



External envelope 479 



Mantle 480 



Respiratory sac 480 



Heart ; : '. . = 481 



Pericardium 481 



Nature of the circulation 481 



Mode of procuring food by means of the respiratory cilia . . . 482 



Alimentary apparatus 483 



Reproductive system '. .; ./. '. .-., , , . 484 



Hermaphroditism of Amaroucium Argus . . . . *.V. f . . 484 



Structure of testes 484 



Structure of ovarium 484 



Composition of the ova 484 



Development of embryo 484 



Structure of larva 484 



The compound Ascidians at first solitary 485 



Growth of the compound Botrytti 485 



Generative system of Cynthia ampulla 486 



Ascidia grossularia 487 



Nervous system 487 



SALP^E Anatomy of 487 



Alternate generations of isolated and concatenated Salpa . . . 488 



Observations of Chamisso, Krohn, Steenstrup, Milne-Edwards, &c. 488 



PYROSOMA 490 



POLYCLINUM 490 



CHAPTER XX. 

 CONCHIFERA. 



CONCHIPERA General survey of the class 491 



OSTRACEA Anatomy of Pecten Jacob&a 491 



Mantle 491 



Branchiae 492 



Arrangement of the viscera 492 



Branchial cilia mode of procuring food 493 



Alimentary system of the Oyster 493 



Respiratory apparatus 494 



Structure of heart and arrangement of the vascular system . . . 495 



Locomotive apparatus structure of the " foot " 496 



Uses of the "foot" 496 



in the Solenida 496 



Pholades 497 



Cardiaceee . ' . . . 497 



Byssus '". ... ,...'. . . 497 



Formation of the byssus in the Mussel 497 



Varieties in the structure of the byssus . . . '..'..' f -. . . 498 



Mechanism for opening and closing the shell . .''/".. -. . . 498 



Hinge .?*?': . . 498 



Adductor muscle .'..,'.,'.-. . . . 498 



Growth and formation of shells .'...- .' . 499 



Structure of the glandular margin of the mantle 499 



Superficial enlargement of the shells 499 



Lines of growth 499 



Formation of ridges, spines, &c 500 



Deposition of coloured pigment 500 



