Volvox in South Africa. 527 



Results of the Investigation. 



Mr. Steer's material proved exceptionally favourable in many 

 respects, and, as a result, not only has it been possible to obtain full 

 details as regards the structure and habits of the two South African 

 species in question, but also to extend our knowledge of the genus 

 Volvox as a whole, filling up several gaps in the life-history. The 

 most important of these are the following : 



1. Changes in the daughter colony and its component cells on 

 completion of cell division preparatory to and during inversion. 



2. Inversion of the " male colony " formed by division of the male 

 initial cell to form the sperm globoid. 



3. Formation of a free, motile zoospore as the result of the germina- 

 tion of the oospore. 



4. Development of this zoospore to form a new colony, which 

 inverts on completion of cell division. 



5. Form and structure of the resultant young colony, the 

 " juvenile " form. 



Methods. 



As already mentioned, the main investigation has consisted of 

 detailed observation of living material. The author was, un- 

 fortunately, not successful in establishing vigorous permanent Volvox 

 cultures (cf. Klein's observations of the capriciousness of Volvox in 

 captivity : " . . . cultures, so successful the previous year . . . 

 failed . . .," 1890, p. 2), hence visited Mr. Steer's garden at frequent 

 intervals for Volvox Rousseletii, noted the amount and state of 

 Volvox in the various tubs and pools, made collections of the material 

 and examined it in greater detail as soon after as possible. In cool 

 weather it could be kept healthy indoors for some days or even weeks, 

 but in summer it soon became abnormal and degenerated, cf. again 

 Klein (1889 a, pp. 45-46). 



The same was done in the case of vleis on the Cape Flats ; in the 

 collections from the latter, however, degeneration was usually more 

 rapid, probably largely owing to the greater wealth of animal life 

 present. In both cases, colonies of various kinds were placed in a 

 watch-glass of water to avoid the distortion due to the weight of the 

 colony resting on the slide (in the case of large colonies this is con- 

 siderable even in a comparatively big drop of water), and measured 

 under the microscope. Many photographs were taken of the colonies 

 as a whole under low powers of magnification ; this necessitated the 

 killing of the colonies to prevent movement, the method used being 



