. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. SEX DETERMINATION IN STEGOPHRYXUS 27 It was found that males of 2 and over could he termed "adult"' as judged by the length and development of the testes and the presence of spermatozoa in the vasa deferentia. In such males the reproductive organs are seen as a pair of long tubular masses, beginning in the first thoracic segment, and extending back into the seventh thoracic segment. The testes lie dorso-laterally adjoining the two liver tubes, one on each side of the animal, except for the anterior extre
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. SEX DETERMINATION IN STEGOPHRYXUS 27 It was found that males of 2 and over could he termed "adult"' as judged by the length and development of the testes and the presence of spermatozoa in the vasa deferentia. In such males the reproductive organs are seen as a pair of long tubular masses, beginning in the first thoracic segment, and extending back into the seventh thoracic segment. The testes lie dorso-laterally adjoining the two liver tubes, one on each side of the animal, except for the anterior extremity of each, which occupies a ventro-lateral position in relation to the liver. In the sixth and seventh thoracic segments, the testes become vasa deferentia which open separately to the outside on the ventral surface of the seventh thoracic segment. The beginning of the vas deferens is often dilated to act as a temporary seminal vesicle. The cells that make up the testis in the anterior-most portion of the organ are all of one type and equally distributed throughout the cross section. Elsewhere, spermatocytes, spermatids, and" spermatozoa may be seen arranged in three distinct zones: spermatocytes in the inner zone next to the liver, spermatids in the middle, and spermatozoa in the outer zone (Fig. 4). The cells of the inner and middle zones are grouped into areas or patches, but those of the outer zone extend without interruption the entire length of the TESTIS LIVER FIGURE 4. Right half of transverse section through the third thoracic segment of a male Stcgophryxus hyptius measuring mm. in length. The testis, dorso-lateral to the liver, shows the characteristic zonal arrangement: spermatocytes in the inner zone closest to the liver, spermatids intermediate in position, and spermatozoa in the outer zone. X Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appeara
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
