440 PROCEEDINGS OF THE 



has said : " The reduction of the enormous catalogue of species 

 of Diatomaceae is a consummation devoutly to be wished." I 

 am not so sure that it is to be so devoutly wished as that. It 

 seems to me that the careful labour of registering minutiae and 

 the consequent subdividing of Diatom systematics has been both 

 fruitful and inevitable. What we should rather wish for is not 

 a curtailing of the differentiating operations, but a process of 

 synthetic integration, undertaken, and only possible, after the 

 study of variations has been thoroughly carried out. The varia- 

 tions of intermdiate forms of Diatoms are by no means abrupt ; 

 they pass insensibly from one form into another. An attempt 

 at synthetic integration forms the subject of this paper. 



An American fossil freshwater Diatom — Navicula Monmouth- 

 iana — may be considered as an ancestral form of a whole series 

 of Cymbella species. This ancestral form seems to have passed, 

 through the coui'se of many centuries, through a long series of 

 slight transformations, evolving several forms of Cymbellae ex- 

 tremely similar to each other, and closing the series at a very small 

 form called Cymbella microce-phala. 



Sir Nicholas then pointed out by means of lantern slides the 

 gradual evolution through various intermediate forms of Cymbella 

 microcefhala from N . Monmouthiana, describing in detail the 

 various points of similarity and difference between one member 

 of the series and the next. A series of nineteen drawings of the 

 various species and varieties dealt with was also shown. 



After remarks had been made by the President and Messrs. H. 

 Morland, N. E. Brown, D. Bryce, and Dr. Leeson, a hearty vote 

 of thanks was accorded to Sir Nicholas Yermolofi for his inter- 

 esting paper. 



The President then called upon the Secretary to read Prof. 

 G. S. West's paper, " A Further Contribution to our Knowledge 

 of the Two African Species of Volvox." In 1910 the author 

 described, from vegetative individuals only, two species of African 

 Volvox, F. Rousseletii and V. Ajricanus. Since that time their 

 sexual colonies have been discovered. Unfortunately, no male 

 colonies of F. Ajricanus were present in the new material, but 

 both male and female colonies of F. Rousseletii were abundant. 

 Prof. West gives a table showing the characters of the two species 

 and then makes an interesting comparison between them and the 

 two well-known European species, F. globator and F. aureus. 



