400 Beard, Heredity and the epicycle of the germ-cells. 



happened 1 ). This law really demands, that there shall be no in- 

 breeding. 



But there is another aspect of Gal ton's law, and this arises from 

 the following- embryological facts. The reduction of chromosomes was 

 probably in its origin merely an undoing of the previous union, and 

 even now it is not the halving of a unit, but of two such. Therefore, 

 it is not a reversion to half cells or half entities or individualities, but to 

 whole ones (Strasburger). From this it follows, that at fertilisation we 

 have to deal with the union of two individualities; of two complete lines of 

 ancestry. The union of these is continued in the primary germ-cells, 

 as evidenced by their duplicated nuclei, until the initiation at least of 

 the ensuing determination of sex, and the united lines are broken up 

 in two separate complete lines, not necessarily identical (like two 

 strings of many coloured beads) with the original two, at the ensuing 

 sex-determination and reduction. 



All along the line from the fertilised egg to that primary germ- 

 cell, which unfolds as an embryo, this duplication is evident and, of 

 course, it must at first be in this cell too. As I have recognised in 

 lectures, there must be a competition between the two components of 

 the duplicated nucleus, when development begins 2 ). This will be such, 

 that of the total nuclear constituents, which together make up the in- 

 herited characters of the two lines, one half must be suppressed, or 

 remain latent, in the development. If these characters be symbolised 

 by the letters of the alphabet in such a way, that the first half of 

 these represent the characters of the one line, the second half those 

 of the other, in the development of the embryo only half of this total 

 can be made use of. Where one letter drops out, its place is occupied 



1) W. K. Brooks has already drawn attention to this matter. He points 

 out that Gal ton's theory demands absence of relationship among all the an- 

 cestors, lie then goes on to show, that in the case of three persons living 

 on a small island their known ancestry goes back 78 generations. The 

 maximum number of distinct ancestors for all three persons together should 

 be 1146, according to Brooks. Of these 452 are recorded, but these are not 

 452 distinct persons, being in fact only 149 (The Foundations of Zoology, 1899, 

 p. 143145). 



2) Haecker has quite recently referred to this in the following words: 

 n Eine ahnliche Konkurrenz koimnt vielleicht auch in den Bildern aus den 

 Gonadanlageu von Diaptomus zum Ausdruck, und wiirde fiir das Verstandnis 

 mancher Vererbungserscheinungen (Dorninieren des einen Elters) von Bedeutung 

 sein". Anat. Auz., V. 20, p. 451. 



I make no comment whatever upon the foregoing, but leave it to the 

 reader to determine the extent of the agreement between Haecker's brief 

 and vague statement and the ideas and conclusions developed in the text of 

 the present writing. 



