238 Professor W. Bateson [Feb. 15, 



geometrical relations to the axes of the body are commonly main- 

 tained, whereas in gjametic repetitions they are commonly lost. 

 (Observe that in Barley, though the embryos stand in definite rows, 

 back to back, each embryo may be either a right-handed or a left- 

 handed screw.) 



The phenomena of heredity are obviously related to those of 

 symmetry and polarity exhibited in the repetitions of parts so 

 characteristic of zygotic structures. Remarkable, and doubtless 

 significant, distinctions exist between animals and plants in these 

 respects. Plants which are mosaics or patchworks, presenting a 

 mixture of allelomorphic characters not siihordinated to geomptrkal 

 control, are usually incapable of being bred true. The geometrical 

 disorder is an indication that the distribution is a mere fortuitous 

 collocation of dissimilar elements, and not a genetically transmissible 

 pattern. Some of the gametes in such a plant will carry one or other 

 of the components ; others arising themselves as mosaic cells may 

 repeat the mixture (cf. mosaic Azaleas, Carnations, the Bizarria 

 Orange, etc.). Animals, however, having mosaic patterns may often 

 be readily established as pure breeds (Sheeted Cows, Dalmatian Dogs, 

 White Bantams, having one or more small grey ticks, etc.). The 

 geometrical relations of gametes to zygotes are therefore quite distinct 

 in animals and plants. 



The geometrical phenomena of gametes are so far quite in- 

 sufficiently studied. In some animals the spermatozoa are all right- 

 handed, in others they are all left-handed ; very rarely there is a 

 mixture (Rat). 



Remarkable phenomena of polarity are exhibited by the " giant 

 forms" best known in certain plants. Just as a zygote can divide 

 to form a twin-pair, so can the material which normally is distributed 

 as two plants be compounded as a single " individual." The case 

 most studied is that of Primula sinensis, described by R. P. G-regory. 

 On at least two occasions " giant " plants containing double the usual 

 number of chromosomes have arisen. Both of these sets of giants 

 exhibit the unique property of being totally unable to breed with 

 the plants from which they were derived, though fertile with other 

 giants. Similar cases are known in Banana (Tischler). Species of 

 Chrysanthemum are described as having respectively 9, 18, 27, 3(1, 45 

 chromosomes. Geoffrey Smith and others have observed giant 

 sperms in animals which presumably contain extra chromosome 

 material. 



Marchal succeeded, by an ingenious method, in raising giant 

 mosses containing double the material proper to a normal plant. 



By virtue of its powers of grouping material around definite axes 

 the zygote can be formed of less than the normal amount of material, 

 or of more than the normal amount; and gametes can at all events 

 exemplify this latter power, inasmuch as they may be compounded of 

 multiples of the normal amount. 



