Proceedings of the Ohio State Academy of Science 329 



unie. In the jji-imitive forms conjugation was probably devel- 

 oped mostly for protection. It preceded an encysted resting 

 condition. In the lower algae Sphaerella, Spirogyra, Ulothrix, 

 and Vaucheria are examples. In the higher plants the conjuga- 

 tion was finally followed shortly by germination because the 

 gametes are protected in the tissue of the parent. Thus in the 

 higher plants and animals conjugation often appears to have a 

 very different purpose from its primitive significance, since it 

 appears here to be especially a stimulus to further growth. 



In the algae it is evident that the purpose of sexuality was 

 not to obtain the advantage of a double number of chromosomes, 

 for in most of the lower forms the number is reduced as soon as 

 the zygote germinates. If, however, there is a mixture of the 

 maternal and paternal chromosomes such temporary conjugations 

 of nuclei may be important in inducing greater variation. But 

 by continued conjugations all the more important combinations 

 v/ould finally be accomplished and sexuality would thus have a 

 tendency to produce uniformity. Of course, it is probable that 

 the original conjugations w^ere merely cytoplasmic, the two nuclei 

 learning to fuse but gradually. 



Our hypothesis, then, is that organisms learned to conjugate 

 through the taking of food, the weaker from the stronger. When 

 this habit was established it led to other habits, the plants which 

 were able to conjugate obtained the advantage at the approach of 

 adverse conditions, because they were thus enabled to reduce 

 their numbers by one-half and the resulting cells could pass more 

 readily into a resting stage because of the greater density of the 

 protoplasm. Finally the mixing of chromosomes in conjugation 

 had an influence on hereditary transmission. Conjugation then 

 is a purposeful process and an advantage to the individual. The 

 habit is acquired and developed like any other instinct. It be- 

 comes a protoplasmic memory, an hereditary character. 



As stated above, outside of the brown and red algae there 

 is only a temporary association of the double number of chromo- 

 somes in the lower green plants, and there seems to have been 

 a gradual devel()]mient of the diploid sporophyte in the higher 

 plants not because of the advantage coming from the greater 



