physiology; symbiosis 419 



Table 25 



Type of reaction and differences of amounts of cis-jtrans- 

 crocetin dimethyl ester in C. eugametos {after Moewus) 



95/5 85/15 75/25 65/35 35/65 25/75 15/85 5/95 

 ?4 ?3 ?2 ?i c^i c^2 S3 SA 



95/5 0/0^ 



?4 o 



85/15 10/10 



$3 o 



75/25 20/20 



$2 I 



25/75 70/70 60/60 50/50 40/40 10/10 0/0 10/10 20/20 



$233330001 



^ The top line represents the differences in the respective cis-/trans- ratios 

 between the left-hand column and the extreme top line. 



It will be noted that no gametic union takes place if the differ- 

 ence in ratio is 0/0 or 10/10. A difference in ratio of 20/20 yields a 

 type I reaction, a 30/30 difference a type 2 reaction and difference 

 of 40/40 or more produces a type 3 reaction. 



The essential details in the scheme (Raper, 1932) (see page 420) 

 show the chemical nature of the sex hormones, which are funda- 

 mentally carotinoids, that has been established, and furthermore 

 it is suggested that certain genes (symbols at sides of arrows) are 

 actually responsible for the various steps in the transformation 

 from one hormone or its precursor to another. 



It should be noted that crocin as a flagellar hormone is ap- 

 parently specific for Chlamydomonas eugametos. There is said to be 



