Volvocacece 



193 



often remain within the old mucous investment of the mother- 

 cosnobium for some time, and the 16-ciliated colonies present the 

 appearance of a composite coenobium. 



K 



Fig. 76. A H, Pandorina morum (Miill.) Bory; A, adult colony; B, group of 

 daughter-colonies within the swollen mother-cell-wall; from near Bradford, 

 W. Yorks. (x475). C H, formation of zygospore (z) and its development 

 (after Pringsheim). K, Stephanosphcera pluvialis Cohn, ordinary vegetative 

 colony (after Hieronymus, x 320). g, gamete. 



Asexual reproduction is by zoogonidia of a precisely similar 

 nature to the cells of Chlamydomonas 1 . The zoogonidia arise by 

 the longitudinal division of the contents of the mother-cell, and 

 each one secretes in addition to its own membrane a gelatinous 

 investment which ultimately forms the common investment of the 

 colony. Schroder 2 has also described an asexual method of repro- 

 duction in which the zoogonidia loose their cilia, vacuoles and 

 pigment-spots, and form a new colony. The gametes arise by the 

 division of the cells into 16 or 32 parts, and they exhibit con- 

 siderable variability in size. Sexual reproduction occurs by the 

 fusion of a pair of gametes, sometimes by the fusion of a smaller 

 active (male) gamete with a larger and more sluggish (female) 



1 Dangeard in Le Botaniste, vii, 1900. 



- B. Schroder in J. B. Schles. Gesellsch. Vaterl. Cult. 1898, Zool., hot. sect. 



W. A. 13 



