JO KRISTINE -BONNEVIE. 



In the telophase the chromosomes grow longer and thinner, 

 their longitudinal split often disappearing ; and small drops of 

 hyaloplasm are seen accumulating at the side of each of them, or 

 between two neighboring chromosomes (lat. anaph. of 2d mat. 

 div.). Through the growth and fusion of these vacuoles the 

 female pronucleus l is formed ; and the chromosomes, invariably- 

 adhering to the surface of the vacuoles, soon lose their staining 

 power so that they cannot be distinguished within the resting 

 pronucleus. 



Early Cleavage Divisions. 



In the early prophase of these divisions the chromatic substance 

 of the nucleus appears in form of an irregular network, which, 

 however, soon proves to consist of a number (28) of cross-shaped 

 chromosomes, each with four equally long arms without any 

 longitudinal split, and many of them with a conspicuous thicken- 

 ing at the center (earl, proph. of earl, cleav. div., p. 62). 



These crosses, attached on the young spindle by their middle- 

 point, are in later stages transformed into V-shaped, longitu- 

 dinally split chromosomes — a transformation, which can only be 

 due to an approach of two arms of the primary crosses on each 

 side of their point of attachment. 



The metaphase of these divisions differ from the maturation di- 



(1887), both referred to in my final paper (1906, p. 390),— and besides these also 

 those of Hof (1898) and Merriman (1904) on vegetative cell-divisions in plants. 



According to observations, to be published in a following paper, I can now say, 

 from my own experience, that this doubleness, occasionally mentioned as occurring 

 outside of the maturation period is (with exception perhaps of Van Beneden's obser- 

 vations in the segmentation divisions of Ascaris), something quite different from the 

 doubleness of the chromosomes at the end of the maturation period first found by me 

 in Enteroxenos — and now also in Nereis, Thalassema and Doris, 



What Hof (1898) has seen in "den eben fertig gebildeten Tochterkernen," is 

 the same structure, which is later described by Merriman (1904). She, however, 

 neither has, nor pretends to have, seen a real doubleness of the daughter chromo- 

 somes ; and her comparison with the maturation phenomena consists in suggesting 

 that also the doubleness so often described at this stage should be (p. 202) " due to 

 the changing of the daughter- chromosomes from tubular structures into the quadri- 

 partite threads." 



I must, therefore, insist upon the priority of having shown a doubleness of the 

 chromosomes at the end of the maturation divisions. After the appearance of my pre- 

 liminary account (1905), however, similar structures were shown to exist in Myxine 

 (Schreiner, 1905), va Ascaris mystax (Marcus, 1905) and in Dytiscus (Schafer, 1907). 



1 The male pronucleus also develops at the same time and in a similar way. 



