246 



THE THEORY OF THE GENE 



mycelia from these two varieties, and eacli myceliiun of 

 such hybrid origin will behave in a manner similar to that 

 shown by mycelia from a single source, in that two given 

 mycelia form clamp connections only in case they carry 

 no factors in common. 



Here we have the phenomenon of sex exhibited on a 

 grand scale if we interpret the factors involved as sex 

 factors in the conventional sense. There is no objection 

 to using the word in this way if it seems advantageous to 

 define sex on such a basis. Personally, I think it is simpler 

 to interpret the results in the same way that East has 

 interpreted the results of his tobacco investigations, and 

 call the factors involved self-sterility factors (see below). 

 The explanation is the same in principle, whatever lan- 

 guage one prefers to use in describing them. 



Under the title of Research on Relative Sexuality, Hart- 

 mann has recently described results that he obtained with 

 the marine alga, Ectocarpus siliculosus. The motile 

 swarm-spores set free from the plants are externally 

 alike, but according to their subsequent behavior they 

 fall into two classes ''females" and "males." The former 



Fig. 137a. 

 Swarming of male gametes around a "female" gamete (to left). 

 Union of "male" gamete and a female gamete (to right). (After 

 Plartmann.) 



