586 ROBERT T. HANCE 



embryo possessing twenty-two chromosomes he found a cell with 

 twenty-three chromosomes and in a twenty-one chromosome 

 Chalinidea embryo a twenty-two chromosome cell was found. 

 Morrill noted this difference in size and stated that the chromo- 

 somes of the embryo started out long and shortened as the 

 embryo became older. 



In Seller's paper ('14-' 15) on the cytology of Lepidotera some 

 figures of somatic chromosomes are quite noticeably larger than 

 are the spermatogonial chromosomes. The number is the same. 



Wieman ('13), in his very clear somatic figures taken from a 

 human embryo, found the number of chromosomes to vary, 

 and he pointed out that, "it is also known that the somatic 

 mitoses do not always show a number identical with the pre- 

 meiotic one." He reviews other similar cases which I have 

 omitted. 



In a paper on the Wandering Jew ('15) I called attention 

 to the morphological difference between the somatic and the 

 germinal chromosomes, the former being much more elon- 

 gated. This may not be an entirely fair comparison, however, 

 as the pollen eventually aborts and the behavior of the pollen 

 chromosomes is pathological. In a study I have been making 

 of the Oenothera mutant scintillans the somatic chromosomes 

 have a wide range of number (from 15 to 21) in the cells of the 

 same plant. It has been possible to show in this case, by special 

 methods developed for the analysis of the chromosomes, that 

 the 'extra' chromosomes are the product or result of fragmen- 

 tation of the longer chromosomes, that the fragments divide 

 regularly and that the total length of the chromosomes in the 

 cells possessing extra chromosomes is the same as that of the 

 type group. The relation of the somatic to the germinal chromo- 

 somes has been conclusively shown. 



In his book, Heredity and Environment, Conklin ('15) has 

 made a statement that would seem to sum up the suggestions of 

 Wieman and which expresses my own belief. " Differentiations 

 of cells are not due to the differentiations of their nuclei, but 

 rather the reverse is true ; such differentiations of nuclei as occur 

 are due to differentiations of the cytoplasm in which they lie. 



