CONTINUITY OF THE CHROMOSOMES 



133 



The grouping of the chromosomes derived from the male and female 

 parents which is to be seen in the first few cleavage divisions is of course 

 an example of gonomery, such as occurs in Cyclops, etc. (Fig. 35), and, 

 as usual, disappears in later cleavages. The important fact is that the 

 two types of chromosomes introduced by the two parents, though mingled 

 together, are recognizable in all mitoses. From this we conclude that 

 their loss of identity in the resting nucleus is apparent only, and not real. 



In the Lepidopteran cross Lycia hirtaria x Ithysia zonaria (Harrison 



B 



Fig. 63. 



Fertilization of the egg of Ascaris megalocephala bivalens by spermatozoa of A. m. univalens. (After Herla, 

 A.B., 1895.) A, approach of the gamete nuclei; B, the chromosomes of the zygote nucleus; C, egg divided 

 into two blastomeres ; D, twelve blastomeres. 



and Doncaster, 19 14) the large chromosomes of Lycia and the small 

 ones of Ithysia are distinguishable in the hybrid right up to the formation 

 of its gametes (Fig. 185). ' 



The persistence of an unusual number, though not of distinct types, 

 of chromosomes in a hybrid was observed by Herla in 1895. He found 

 five females of Ascaris megalocephala bivalens which had been fertilized 

 by the univalens variety. Consequently the nuclei of their hybrid embryos 

 had three chromosomes, two derived from the female and one from the 



