1904] MONTGOMERY — CELLULAR BASIS OF HEREDITY. 5 



THE MAIN FACTS IN REGARD TO THE CELLULAR 

 BASIS OF HEREDITY. 



(Contributions from the Zoological Laboratory of the University of Texas, 



No. 56.) 



BY THOMAS H. MONTGOMERY, JR. 



(Read January 15, I904..) 

 I. 



Under heredity we understand the transference to the offspring 

 of qualities of the parent or parents. The interpretation of the phe- 

 nomena involved constitutes one of the broadest problems in the 

 field of Biology, and has for centuries been the theme of eager dis- 

 cussion. Yet only in the past forty years has there come out any 

 positive knowledge upon the subject, except the making known of 

 certain cases of parthenogenesis and of the occasional difference of 

 reciprocal crosses. 



There are obviously two methods of determining the facts of 

 heredity. First, by the intercrossing of different varieties or 

 species, and the determination of the relative influences of the 

 parents upon the offspring. The first fundamental work in this line 

 was done by Mendel in 1865 {Versuche iiher Pflanzenhybriden), 

 who determined a large series of facts for the plant genus Fisum, 

 and from the data established a mathematical law for this genus as 

 to the inheritance of parental qualities by the hybrids. This 

 memoir, only some three years ago resurrected from its long 

 obscurity, is to-day occupying the attention it deserves, and has 

 stimulated much work along the same line. De Vries' magnifi- 

 cent work, Die Mutatiotutheorie , demands as well recognition in 

 this respect. But it is clear that such experimental intercrossing, 

 in so far as only the end results of the crosses are considered, can 

 do no more than state the degrees of resemblance of the offspring 

 to the parents, and decide the questions as to the fertility of the 

 hybrids. Important and necessary as it is, it does rot go to the 

 root of the matter, and cannot present any empirical analysis of 

 the underlying factors. 



For an understanding of these we must turn to the second method, 

 to the examination and interpretation of the intimate structural 

 and growth phenomena of the germ cells themselves, that is, to the 



