THE CHROMOSOMES OF THE OPOSSUM, DIDELPHIS VIRGIMANA

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Abstract
The chromosomes of the American opossum were studied in short term cultures of cells from one to three-months-old animals. The diploid number was 22, in agreement with previous reports. There were two main groups of autosomes, one consisting of 6 pairs of chromosomes with subterminal centromeres and the other of 4 pairs of acrocentric chromosomes. There was a gradual gradiation in the lengths of the autosomes, so that it was difficult to identify with certainty individual elements within a group. The sex chromosomes were smaller than any of the autosomes and the Y chromosome was about half as long as the X. The X chromosome had a submedian centromere and the Y chromosome a nearly terminal centromere.