CHROMOSOMES OF INDIAN RUNNER DUCK. 343 



there is in the group of seven, one chromosome which is larger 

 than the others which has the characteristic form of the largest 

 odd chromosome in the cells of the female, large at one end and 

 taper at the other. 



Schiwago (1924) has recognized gonomeric grouping in the 

 cells of the domestic chicken. (I have taken the liberty of re- 

 producing some of his drawings as well as those of Hance from 

 the same form and two from Painter from the lizard). The 

 lettering of the chromosomes in Figs. 32 and 33 are as Schiwago 

 gave it. The same grouping is apparent in the work of Hance 

 and Painter although the authors do not point out the fact. I 

 have again taken the liberty to draw a line through each of these 

 figures (Figs. 30, 31, 35, 36) which might suggest a possible 

 separation of the chromosomes into maternal and paternal 

 groups. 



D. H. Tennent (1908) found gonomeric grouping when working 

 on the eggs of Toxopneustes and Arbacia fertilized with Moina 

 sperm. Margart Morris (1914) in her work on hybrids between 

 Fundulus and Ctenolabrus found a somewhat similar condition. 

 Many other instances of this phenomenon among different 

 species are on record. 



Gonomery represents no more than a tendency on the part of 

 the chromosomes to remain in separate maternally and paternally 

 derived groups during a part of the early development. Con- 

 sidering these facts, such a phenomenon in the duck w^ould seem 

 to afford a valuable check on the count of the chromosomes, as 

 well as a check on the number contributed by each sex, especially 

 with respect to the large chromosomes, since these are so well 

 defined that they may be readily recognized. 



FILAMENTOUS LINKAGE. 



Filaments which seemed basophylic in character were found 

 connecting chromosomes in somatic cells in prophase stages. 

 Not all groups of chromosomes formed by such fastenings were 

 constant. Some groups composed of definite numbers were 

 found a sufficient number of times to justify one in concluding that 

 they might be relatively constant. In nearly all cases the groups 

 are made up of chromosomes of the intermediate and smaller 



