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5. Volvox in South Africa. By M. A. POCOCK, Ph.D., F.L.S. 

 (With Plates XXXVIII-XLIX and 10 Text-figures.) 



CONTESTS. 



PAGE 



Introductory ........... 525 



Aim and Results of Investigation ....... 526 



Methods 527 



Occurrence of Volvox in Africa ........ 529 



Habitat of Volvox in Africa. ........ 530 



V '. Rousseletii and V. capensis. I. The Adult Form ..... 531 



Distinguishing Features . . . . . . . . .531 



Parasites of Volvox .......... 533 



Macroscopic Observations ......... 534 



Movement ; Phototactism ......... 535 



Sequence of Asexual and Sexual Phases ...... 538 



Observations on the Cape Flats ........ 539 



Constitution and Size of the Coenobium ...... 543 



The Somatic Cell 546 



1. Size of Cell 547 



2. Cell Membranes 548 



3. Protoplast, Form and Structure ....... 550 



(i) Nucleus .......... 551 



(ii) Chloroplast ......... 552 



(iii) Pyrenoid. ......... 552 



(iv) Cilia .......... 553 



(v) Eyespot .......... 554 



(vi) Protoplasmic Connections . . . . 556 



(vii) Contractile Vacuoles. ....... 558 



Entity and Interdependence of the Somatic Cells ... . 559 



Change in Appearance as Coenobium Ages . . . 559 



Cell-structure compared with that of V. globator . . . . 560 



Reproduction ....... ... 560 



Number and Arrangement of Reproductive Cells .... 562 



A. Asexual. .......... 562 



B. Sexual, Male ... 564 



C. ,, Female ......... 565 



Development of Reproductive Colls ....... 566 



A. Gonidiuin .......... 566 



Enlargement ......... 566 



Division .......... 567 



Period of Re-orientation ....... 571 



(a) Preparation ........ 572 



(b) Inversion . ...... 574 



