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| | | #REDIRECT [[Paper - The early development of the cat (1924)]] |
| ==Introduction==
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| Our knowledge of the early development of the Cat, as indeed of the Carnivora in general, is singularly incomplete. Th. L. W. Bischoff, in his classical monograph ' Entwicklungs- geschichte des Hunde-Eies ' published in 1845, provided the first account of the development of a Carnivore from the unsegmented egg onwards and, considering the date of his work, his achievement was really a remarkable one. In addi- tion to later embryonic stages, he described and figured a series of segmenting ova and blastocysts of the Dog, with such fidelity and accuracy that his account is, even to-day, of the greatest interest and value. He recognized and figured the germinal vesicle of the full-grown ovarian ovum and the refractive granules (' Dotter ') present in the cytoplasm of the latter. He observed the persistence of part of the discus proligerus round the unsegmented tubal egg, and noted its thick zona and the numerous sperm-heads imbedded in it. He figured the two-celled egg with what are evidently two polar bodies situated in the plane of cleavage. He described and figured the three-celled and four-celled stages, his figures of the latter showing quite accurately the characteristic cross- shaped arrangement of the blastomeres. He figured three later tubal eggs, said to be composed of eight, ten, and eighteen blastomeres respectively, and he also illustrated and described a series of morulae and blastocysts from the uterus. He recognized the delicate membranous wall of the blastocyst lying inside the zona and also ' den runden und gleichmassig dunkeln Fruchthof ', and since he found that the latter is situated in the former, he termed this vesicular stage ' die Keimblase '.
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