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Studies in Spermatogenesis Part I   By: (1861-1912)

Studies in Spermatogenesis Part I by Nettie Maria Stevens

First Page:

STUDIES IN SPERMATOGENESIS

WITH ESPECIAL REFERENCE TO THE

"ACCESSORY CHROMOSOME"

BY N. M. STEVENS.

[Illustration]

WASHINGTON, D. C.: Published by the Carnegie Institution of Washington September, 1905.

CARNEGIE INSTITUTION OF WASHINGTON

PUBLICATION No. 36

FROM THE PRESS OF THE HENRY E. WILKENS PRINTING CO. WASHINGTON, D. C.

STUDIES IN SPERMATOGENESIS WITH ESPECIAL REFERENCE TO THE "ACCESSORY CHROMOSOME."

By N. M. STEVENS.

In connection with the problem of sex determination it has seemed necessary to investigate further the so called "accessory chromosome," which, according to McClung ('02), may be a sex determinant. This view has been supported by Sutton ('02) in his work on Brachystola magna , but rejected by Miss Wallace ('05) for the spider.

The forms selected for study have been taken from several groups of insects, and are all species whose spermatogenesis has not been previously worked out. They are (1) a California termite, Termopsis angusticollis ; (2) a California sand cricket, Stenopelmatus ; (3) the croton bug, Blattella germanica ; (4) the common meal worm, Tenebrio molitor ; and (5) one of the aphids, Aphis oenotheræ .

A brief account of a chromatin element resembling the accessory chromosome in Sagitta has been added for comparison. The spermatogenesis of each form will be described in detail, and a general discussion of the results and their relation to the accessory chromosome and sex determination will follow. The spermatogenesis of the aphid has been included in another paper, but a summary of results and a few figures will be given here for reference in the general discussion.

METHODS.

The testes were fixed in various fluids Flemming's strong solution, Hermann's platino aceto osmic, Gilson's mercuro nitric, Lenhossek's alcoholic sublimate acetic, and corrosive acetic. Flemming's and Hermann's fluids followed by safranin gave good results in most cases. The mercuro nitric solution and Lenhossek's fluid gave excellent fixation and were preferable to the osmic mixtures when it was desirable to stain the same material with iron hæmatoxylin, and also with various anilin stains.

Heidenhain's iron hæmatoxylin, either alone or with orange G or erythrosin, was used more than any other one stain. With osmic fixation safranin gave better results in some cases, because of the abundance of spindle fibers and sphere substance which were stained by hæmatoxylin. The safranin gentian combination used by Miss Wallace and others in the study of the accessory chromosome did not prove to be especially helpful with these forms. Thionin was found to be a very useful stain for distinguishing between the accessory chromosome and an ordinary nucleolus. Licht grün was often used in combination with safranin.

RESULTS OF INVESTIGATIONS.

Termopsis angusticollis.

In the termite it was not found to be practicable to dissect out the testes. The tip of the abdomen was therefore fixed and sectioned, young males whose wings were just apparent being used. The cells are all small, and could not be studied to advantage with less than 1500 magnification (Zeiss oil immersion 2 mm., oc. 12).

In the spermatogonium there is a very large nucleolus (plate I, fig. 1), which in the iron hæmatoxylin preparations is very conspicuous, but does not stain like chromatin with thionin or other anilin stains, nor does it behave like an accessory chromosome during the maturation mitoses. Before each spermatogonial division it divides as in figures 2 and 3, and the same is true for each maturation mitosis. Figure 4 shows the 52 chromosomes of a spermatogonial division in metaphase. Figures 5 and 6 are young spermatocytes, showing the division of the nucleolus. Figures 8, 9, and 10 show a stage immediately following that shown in figure 6 and evidently persisting for some time. The spireme thread is very fine, stains deeply, and is wound into a dense ball, often concealing one (fig... Continue reading book >>




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