308 Strasburger . — The Periodic Reduction of 
clear by observations on Ascaris nigrovenosa 1 , that the 
chromosomes of the two parents do not lose their independence 
in connexion with the sexual act. In this Ascaris both the 
sperm-nucleus and the germ-nucleus independently go through 
the prophases of division, and it is only then that the two sets 
of chromosomes arrange themselves in the common spindle of 
the embryonic nucleus. In each subsequent nuclear division 
each half contains a number of chromosomes identical with 
that of the combined parental chromosomes in the fertilized 
ovum. Hence in hybrids the chromosomes of both father and 
mother continue active ; and the behaviour of hybrids shows 
peculiarities which are very instructive for the comprehension 
of the phenomena of heredity in the offspring of legitimate 
unions. Hybrids may exhibit in all their parts a combination 
of the characters of the two parents ; or they may show this 
only in certain parts, whilst other parts present the distinct 
characters of one or other of the parents ; or they, on the 
whole, resemble one parent more than the other ; or, finally, 
they may altogether resemble one of the parents. Naudin 2 
has drawn attention to the fact that, in some hybrids, the 
characters of the two parents, instead of being blended, are 
manifested in patches ; this may occur in all parts of the 
plant, but it is especially marked in flowers and fruits. In 
such a case the hybrid is a sort of mosaic made up of portions 
of the two parents. Millardet 3 has recently given an account 
of hybrids which are more like, or, in the extreme case, 
exactly resemble either the father or the mother. 
The hybrids of mosaic-like constitution may perhaps be 
adduced as evidence in support of the possibility of hereditarily 
unequal division of the nucleus ; and one of the cases de- 
scribed by Millardet, that of a hybrid Vine, known as the 
1 Edouard van Beneden, Rech. sur la maturation de l’oeuf, &c., Taf. XIX, 
bis et ter. 
2 Sur 1 ’hybridite dans les vegetaux, Nouv. Arch, du Museum, I, 1865, pp. 33, 
49 > I51 * 
3 Note sur l’hybridation sans croisement, ou fausse hybridation, Mem. de la 
Soc. d. Sci. phys. et nat. de Bordeaux, t. IV, ser. 4, 1894. 
