205 



In this connection it will be recalled that in 1891 Atkinson 

 suggested that the embryo-sac is to be interpreted as a female 

 prothallus, originating from the nucellus by apospory, but that 

 there is not, therefore, to be inferred any phylogenetic connec- 

 tion with earlier forms, nor that the process of aposporous 

 origin of the gametophyte is continuous through the groups of 

 plants. 



" Mendelisjn and Olhcr Methods of Descejit.'"^ This paper is 

 an elaboration of a discussion of Davenport's lecture on "Heredity 

 and Mendel's Law," delivered before the Washington Academy 

 of Sciences, on February 26, 1907. It is contended that, "the 

 definite mathematical relations which appear in a Mendelian ex- 

 periment arise from the methods of reproduction rather than from 

 the methods of inheritance," and that the inferences as to the ex- 

 istence of character-unit-particles and the purity of germ cells 

 are rendered entirely unnecessary by the interpretations which 

 the author gives to the experimental results of others. 



Descent and heredity are by no means synonymous. There 

 are outlined twenty-two different methods of descent, of which 

 heredity is one, mutation another, and Mendelism another. 

 " Heredity, in the more definite sense, is a fact, but only under 

 conditions of restricted descent." Mendelism is not a form of 

 heredity, but " constitutes a rather wide departure from the pri- 

 mary concept of heredity." It is " one of the methods of descent 

 in which unlike produce unlike." According to Cook, there has 

 been a complete failure, thus far, to demonstrate the Mendelian 

 principles. The terms hybrid and cross seem (p. 223) to be con- 

 sidered as synonyms. 



Although artificial selection has been satisfactorily practiced 

 in horticulture for decades, the author declares that, " generally 

 speaking, the cells which compose the bodies of the higher 

 organisms do not leave any descendants to perpetuate their 

 characters." Mutation and MendeHsm " are not phenomena of 

 evolution, but of degeneration, " and, " when the distinction be- 

 tween discontinuous variation and discontinuous evolution is once 

 appreciated, it will become apparent tbat the mutation theory 



*Cook, O. F. Proc. Wash. Acad. Sci. 9 : 189. 1907. 



