Communication on the attachment and the early development of Macroscelides (=Elephantulus) rozeti Duv., the North-African Junping Shrew
1. In Macroscelides (Elephantulus?) rozeti Duv., a North-African form, the pregnant uterus shows 3 swellings (sometimes this number is reduced to 1 or 2). The South-African form Elephantulus myurus Jamesoni, examined by prof. VAN DER HORST (Johannesburg) always shows two swellings, one in each half of the uterus horns. 2. The tuba is connected with a periovarial sac. 3. The eggs in the ampulla are naked and not surrounded by the zona pellucida. This causes sometimes the segmented cells to be set free. 4. The four-celled stage shows a tetrahedral arrangement. 5. In the uterus horn the unilaminar blastula is formed by the absorption of water. 6. In a stage of 120 cells the blastula-wall separates amoeboid cells into the interior forming a loose reticulum. Afterwards these cells concentrate at one side of the germinal vesicle and form the embryonic knot. 7. This organ separates an entodermal cell-layer at its base. 8. At the mesometrical side the germinal vesicle adheres to the uterine wall which is syncytial at this spot. 9. After the adhering of the germinal vesicle the mucosa uteri becomes very thick and the muscularis very thin. The small number of blood vessels in the mucosa is very remarkable. 10. There is a marked increase of the number and extent of the uterine glands. The image resembles that of the secretory phase in man. 11. In the following stage (N. 45) the trophoblast has become very thick and has penetrated into the mucosa uteri. The embryonic knot shows a large archamniotic cavity. 12. In N. 6 the embryonic region shows 7 à 8 somites. A distinct pharynx is present. In the mid- and hindgut a large connection of enteron and yolk sac is present. Cloaca with allantoic evagination, a large, mesodermal, allantoic rudiment is present. The yolk sac forms about two thirds of the blastocyst, the remaining third part is formed by the exocoel and the amniotic cavity. A proamnion is present. Enlarged uterine glands surround the whole uterine cavity. A large ectoplacenta shows a toadstool-form and penetrates into the uterine wall forming a disc of foeto-maternal symplasma. Heart rudiment rather well developed. 13. N. 8. The embryo shows ± 25 somites. Allantois well developed, adhering to the ectoplacenta. The greater part of the blastocyst is formed by the exocoel. Three visceral pouches are present, the mouth plate is lacerated. The neural tube is completely closed. 14. In N. 1 30-35 somites and 12 nephric tubules are present. Rudiment of anterior extremity, 3-4 aortic arches. 15. In N. 3 the yolk sac is much smaller and its walls are shriveled. A yolk stalk may be seen but the connection between the lumina of gut and yolk sac has disappeared. The allantois surrounds the amniotic cavity and fills up the main part of the blastocyst. It shows four lobes. The ectoplacenta shows a thick layer of labyrinthic tissue at the embryonic side. The embryo is strongly coiled and possesses a distinct torsion. The kidney is well developed (with Malpighian corpuscula). Posterior extremities are present. In the anterior ones the rudiment of the skeleton may be noticed. 16. In the stages N. 45 and N. 1 a distinct mesoplacentarium consisting of numerous lamellae with bloodvessels is present at the mesometrical side of the uterine wall. As in the aguti (BECHER) this phenomenon may be in relation with the jumping propulsion.
|Journal||Bijdragen tot de dierkunde|
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de Lange, D. (1949). Communication on the attachment and the early development of Macroscelides (=Elephantulus) rozeti Duv., the North-African Junping Shrew. Bijdragen tot de dierkunde, 28(1), 255–285.