628 Annals of the South African Museum. 



three days to complete." No further description or drawings are 

 given. 



In F. aureus, Cienkowski (1870) observed germinating oospores 

 as far as the second division and believed that each sphere of seg- 

 mentation eventually became a coenobium. 



Henneguy (1879, p. 93) germinated spores from material collected 

 in a deep basin in the Jardin des Plantes, and describes stages in de- 

 velopment briefly but clearly ; he observed the escape of the spore 

 from the hard exospore, projection of the swollen endospore, division of 

 the spore contents into 2 equal parts, which by successive bipartitions 

 give rise to 4, 8, 16, etc., small cells, thus forming a " blastoderm 

 analogous to the blastoderm of a holoblastic ovum." Inversion 

 was not noticed, but the formation of the cilia within the endospore, 

 subsequent disappearance of the latter, and development of the young 

 colony are mentioned. No reference is made to any difference between 

 the latter and the ordinary adult colony. Kirchner (1879, p. 99) 

 also published an account of germination in F. aureus with figures, 

 and on his paper most of the accounts included in descriptions of the 

 genus are based, e.g. by Pascher (1927, pp. 66, 462), Oltmanns (I, p. 230, 

 figs. 6, 7, 236), Printz (1925, p. 3, fig. 21). Unfortunately Kirchner's 

 paper has not been available in this country for reference, but from 

 the details given by the authors quoted above he adds little or nothing, 

 apart from the diagrams, to the details given by Henneguy. Nowhere 

 is any reference made to the intervention of a "Juvenile " form, and 

 each writer expressly states that no motile zoospore is formed. 



Zimmermann (1921, p. 274) refers to Kirchner for the external 

 course of development, and confines himself to the cytological aspect, 

 finding that the first division is heterotypic and is followed by suc- 

 cessive divisions of the usual type. Thus he too agrees that in F. 

 aureus no motile zoospore is formed, and that all four cells resulting 

 from reduction division combine to form the single young colony. 



Mainx (1929, p. 211) found that in F. aureus in certain conditions 

 oospheres ripened parthenogenetically into oospore-like structures, 

 and that these parthenospores germinated exactly as described by 

 Henneguy, Kirchner, and Zimmermann for the zygote. At the same 

 time Zimmermann's observation of reduction division goes to show 

 that some at least of the resting spores are true zygotes. 



Previous accounts of germination in Volvox, therefore, are all based 

 on only two or three observations of F. aureus and can be taken only 

 as referring to that species, not to the genus as a whole. 



Thus the above account of germination in F. Rousseletii fills a 



