540 
Reginald Ruggles Gates 
1904), Oenothera lata [x — 7) x 0. gigas (x = 14) (Gates 1908a) 
and Ascaris megalocephala biralens [x = 2) x A. meg.univalens [x = 1) 
(Herla, 1893, Zoja, 1895) are to the point. To say that the num- 
ber of chromosomes is the average between those in the somatic cells 
of the parents explains nothing. True, the chromatin mass of the 
hybrid will be intermediate between those of the parents. But this 
leaves unexplained the further fact that the nuinber of bodies is the 
exact sum of those in the particular germ cells frorn which the hy- 
brid arose. The only adequate explanation of this fact is that in 
such cases the chromosomes maintain some sort of morphological or 
physiological independence throughout the life cycle of the organism, 
descendants of eacli of tlie chromosomes which entered the zygote 
appearing finally in its germ cells. Furthermore, according to Rosex- 
berg, in the Drosera hybrid the chromosomes are of two sizes corre- 
sponding to the chromosomes of the parents from which they were deri- 
ved; and Moexkhaus (1904) has shown similar differences in the 
chromosomes of certain hybrid fish embryos. 
Farmer and Digby (1907), in a study of apogamy and apospory 
in Ferns, made a comparison of the size of the cells and nuclei of 
the prothallium, and the antherozoids. In Athyrium Filix-foemina 
and three of its varieties, they found that the measurements were 
saccessively larger in the three varieties tlian in the species and that 
tliere was a corresponding increase in the number of chromosomes, 
the numbers for the species and its varieties being estimated at 
76—80, 84, 90, and 100 respectively. On the contrary, another 
fern, Lastrea pseudo-mas, and three of its varieties only partly follo- 
wed this rule. In one variety in particular the cells and nuclei were 
smaller altliough the chromosomes were more numerous than in the 
type. It should be said, however, that the chromosome numbers in 
the Ferns are high and these counts were in many cases inexact 
approximations. 
A comparison of sporophytes with gametophytes as regards the 
size of their cells and nuclei would be interesting in this connection, 
but usually the tissues of the two are so unlike that tliere is not a 
sufficient basis for comparison. However, in the Algae, and particu- 
larly the Rhodophyceae, the sporophyte and gametophyte are not 
i) One plant in this cross was found to have 20 chromosomes instead of 
21, but a simple explanation for this has already been given. (Gates 1908 b. 
p. 28.) 
