98 SEX IN MICROORGANISMS 



Type A-1 or by Reduced Type B-1. He has also shown (1953b) 

 that in Cocconeis phcenwla var. teimistriata Geitler two metagamic 

 divisions occur. The first division is associated with the formation of 

 the first shell in the auxospore and the second one with the second 

 shell. Geitler and Mack (1953) point out that although in the genus 

 Cymbella there is variation in the relation of the position of the axis 

 of the auxospore and the position of the first shell to that of the 

 mother cell, the arrangement for many species is very definite. Nip- 

 kow (1953) states that he has seen asexual auxospore formation by 

 Reduced Type C-2-b in Fragilaria crotonensis Kitton but does not 

 describe the various steps in the process. 



REFERENCES 



Bergon, P. 1907. Les processus de division, de rajeunissement, de la cellule et de 



sporulation chez le Biddiilphia inobilievsis Bailv. Bull. soc. Botaii. France, 



54, 327-358. 

 Calkins, G. N., and F. M. Summers. 1941. Protozoa in Biological Research. 



Columbia University Press, New York. 

 Fritsch, F. E. 1935. The Structure and Reproduction of the Algae. Vol. I. 



The Macmillan Co., New York. 

 Geitler, L. 1928. Kopulation und Geschlechtsverteilung bei einer Nitzschia — 



Art. Arch. Protistevk., 61, 419-442. 

 . 1932. Der Formwechsel der pennaten Diatomeen. Arch. Protistenk., 



78 [1], 1-226. 

 . 1935. Reproduction and life history in diatoms. Botan. Rev., 1 [5], 



149-161. 

 . 1939. Gameten- und Auxosporenbildung von Synedra ulna im Ver- 



gleich mit anderen pennaten Diatomeen. Planta, 30 [3], 551-567. 

 . 1940. Die Auxosporenbildung von Meridian circulare. Arch. Protis- 

 tenk., 94 [2], 288-295. 

 . 1949a. Die Auxosporenbildung von Nitzschia signwidea und die 



Geschlechtsbestimmung bei den Diatomeen. Portugaliae Acta Biological, 



series A, Vol. R. B. Goldschmidt, 79-87. 

 . 1949b. Beitrage zur Kenntnis der Auxosporenbildung pennater Dia- 

 tomeen. Oster. botan. Z., 96 [3-4], 467-473. 

 . 1951a. Pragame Plasmadifferenzierung und Kopulation von Eunotia 



flexuosa (Diatomee). Osterr. botan. Z., 98 [4], 395-403. 

 . 1951b. Kopulation und Formwechsel von Eunotia arcus. Osterr. botan. 



Z., 98 [3], 292-338. 

 . 1951c. ZelldifTerengierung bei der Gametenbildung und Ablauf der 



Kopulation von Eunotia (Diatomee). Biol. 7.entr., 70, 9/10, 385-398. 

 . 1952a. Die Auxosporenbildung von Rhoicosphenia curvata. Osterr. 



botan. Z., 99 [1], 78-89. 



