X CONTENTS. 



CHAPTER XXXV. TUNICATA continued. PAGE 



The mantle . 355 



The nervous system 357 



The ciliated pit ........ 360 



The chorda 361 



Mesoderm, body-cavity, musculature .... 362 



The alimentary canal 364 



Peribranchial, atrial or cloacal cavity .... 366 



The heart, the pericardium and the epicardium . . 368 



E. Review of the organisation of the free-swimming larva . 371 



F. Fixation and retrogressive metamorphosis . . . . 372 



The development of new gill-slits .... 376 



The development of the genital organs . . . 379 



O. The abbreviated development of the Molgulidae . . 381 



3. Doliolum 382 



4. Pyrosoma 389 



A. Cleavage and formation of the germ -layers . . . 389 



B. Development of the Cyathozooid 393 



C. Development of the primary Tetrazooid colony . . 398 



D. Further development of the Cyathozooid . . . 400 



E. Development of the four primary Ascidiozooids . . 404 



5. The Hemimyaria (Salpidae) 414 



A. Forms without covering folds . . . . . . 423 



B. Forms with covering folds 433 



General considerations on the embryonic development 



of the Salpidae . 445 



II. Asexual reproduction . . . . . , . . . 448 



1. Social and composite Ascidians 449 



A. Reproduction through transverse fission .... 449 



B. Stolonic gemmation 455 



C. Pallial gemmation of the Botryllidae . . . . 458 



D. Budding of the Didemnidae and the Diplosomidae . 459 



E. Development of the organs in asexually produced in- 



dividuals 463 



2. Doliolidae . 470 



Alternation of generations in Doliolum . . . . 476 



Alternation of generations in Anchinia .... 479 



Alternation of generations in Dolchinia . . . . 483 



3. Pyrosoma 484 



A. Development of the proliferating stolon . . . . 484 



B. Further development of the buds 489 



4. Salpidae 494 



A. Structure and development of the proliferating stolon . 495 



B. Development of the buds on the stolon .... 499 



C. Development of the organs in the bud .... 508 

 5; The interpretation of the alternation of generations in the 



Tunicates 512 



III. General considerations on the Tunicates . . . . . 516 



Literature , 524 



