THE ROLE OF STUDY OF ALGAE IN DEVELOPMENT OF BOTANY 477 



of the opposite sex to the filtrate. This caused an immediate agglutination of 

 the gametes, even though gametes of the opposite sex were not present in the 

 filtrate. This behavior to filtrates or centrifugates is not peculiar to Tetraspora 

 but has been found in other isogamous algae with motile gametes, including 

 Botrydium (Moewus, 1940c), Chlamydomonas (Moewus, 1933), Dunaliella 

 (Lerche, 1937), Ectocarpus (Hartmann, 1937), and Protosiphon (Moewus, 

 1933). My studies on various species of Chlamydomonas indicate that the 

 gamone causing an agglutination of gametes of opposite sex is not a chemo- 

 tactic gamone. 



Beginning with the work of Pfeffer, several investigators have shown a 

 chemotactic response of antherozoids of pteridophytes and bryophytes. These 

 investigators assume that entrance of antherozoids into an archegonium is 

 due to a chemotactic substance (gamone) secreted by the egg, but there has 

 been no actual demonstration of this. A secretion of a chemotactic gamone 

 into the surrounding water has been demonstrated for two oogamous algae, 

 Fucus and Sphaeroplea. This was shown for Fucus by taking water containing 

 many eggs, centrifuging, filling capillary tubes with the centrifugate, and 

 placing the tubes in a dish containing swimming antherozoids (Cook et al., 

 1948; Cook and Elvidge, 1951). When this was done there was a clustering 

 of many antherozoids around the end of the tube. Pascher (1931b) devised 

 an ingenious method for demonstrating that eggs of Sphaeroplea excrete a 

 chemotactic substance. Short lengths of white thread were placed in a dish 

 containing female filaments with ripe eggs. After lying in the dish for a time 

 the threads were transferred to a dish containing motile antherozoids. Soon 

 thereafter there was a marked accumulation of antherozoids in the vicinity 

 of the threads. This persisted for an hour or more but then disappeared. 

 Moewus (1939a) has studied the chemotactic gamones of Chlamydomonas 

 eugametos by means of Pfeffer's capillary-tube method. He reports that male 

 and female gametes each secrete a chemotactic gamone and that gamones 

 of the two are not identical. Others have not been able to duplicate his results. 



Attempts to show the presence of termones have centered around reactiva- 

 tion of gametes that have become sexually inactive. In Ectocarpus Hartmann 

 (1937) took female gametes that had become sexually inactive and placed 

 them in a filtrate from sexually active female gametes. When this was done 

 the female gametes became sexually active and fused with male gametes. In 

 a similar manner male gametes were reactivated. These experiments are in- 

 conclusive as demonstrating the presence of termones because it is possible 

 that loss of sexuality by the gametes was due to a loss of gamones rather 

 than to a loss of termones. An activation of sexually inactive cells of Chlamy- 

 domonas eugametos by means of centrifugates from sexually functional cells 

 has been recorded by Moewus (1940a). He identifies the termones as deriva- 

 tives of the carotenoid protocrocin. The termone (gynotermone) of female 

 cells is said to be pikrocrocin. The termone (androtermone) of male cells is 



