The Chromosomes Classic Reprint

Excerpt from The Chromosomes

Hope that this book will be of use to many bio logiste who realize that chromosome-cytology has made considerable progress in the last ten years, and that the existing text-book accounts of mitosis and meiosis are hopelessly inaccurate, but who have no time to read the larger works of Darlington and Belai', which must remain the standard sources of information on the subject.

Chromosome cytology is essentially a practical sub jcet, which can only be thoroughly mastered by a study of actual preparations under the microscope. Unfortunately this study is usually regarded as too difficult to be included in a degree course in biology. It is surprising, however, how much can be seen, even without using an Oil-immersion Objective, provided that one chooses suitable material with large chromo somes. There 18 no doubt that for most purposes the testes of Locusts and Grasshoppers (any species will do) provide the best introductory material. They Should be fixed in Flemming's solution and stained in one of the aniline dyes like Gentian Violet. In the course of the past year I have made the ordinary degree students in this department work through material of this kind (sectioned at 25 It so as to Obtain whole nuclei). They were able to see all the stages of mitosis and meiosis and even to work out the average number of chiasmata per nucleus in three difi'erent species. That it is possible for students to do this in a course involving only one afternoon a week should destroy the myth that cytology is a fantastically difficult subject.

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