50 TEXT-BOOK OF EMBRYOLOGY. 



v 



In the albino rat (Huber) cleavage gives rise to a true morula consisting of 

 from 24 to 32 cells. Subsequent to this there appears among the cells of the 

 morula a crescentic space which gradually enlarges until the cells, being pushed 

 peripherally, form a relatively thin layer around a central cavity. At one point 

 in the wall of this hollow structure (blastocyst, blastodermic vesicle) a little 

 mass of cells constitutes the probable homologue of the inner cell mass which 

 has been described previously. 



References for Further Study. 



ASSHETON, R.: The Segmentation of the Ovum of the Sheep, with Observations on the 

 Hypothesis of a Hypoblastic Origin for the Trophoblast. Quart. Jour, of Mic. Science, Vol. 

 XLI, 1898. 



BLOUNT, M.: The Early Development of the Pigeon's Egg, with Especial Reference to 

 the Supernumerary Sperm Nuclei, the Periblast and the Germ Wall. Biolog. Bull., Vol. 

 XIII, No. 5, 1907. 



CONKLIN, E. G.: Karyokinesis and Cytokinesis. Jour. Acad. Nat. Sci. of Philadelphia, 

 Vol. XII, 1902. 



CONKLIN, E. G.: The Embryology of Crepidula. Jour, of MorphoL, Vol. XIII, 1897. 



EYCLESHYMER, A. C.: The Early Development of Amblystoma, with Observations on 

 Some Other Vertebrates. Jour, of MorphoL, Vol. X, 1895. 



HARPER, E. H.: The Fertilization and Early Development of the Pigeon's Egg. Am. 

 Jour, of Anat., Vol. Ill, No. 4, 1904. 



HARTMAN, C. G.: Studies on the Development of the Opossum. Jour, of Morph., Vol. 

 XXVII, 1916. 



HATSCHEK, B.: Studien iiber Entwickelung des Amphioxus. Arbeiten aus dem zool. 

 Instit. zu Wien, Bd. IV, 1881. 



HERTWIG, R.: Eireife, Befruchtung u. Furchungsprozess. In Hertwig's Handbuch d. 

 vergleich. u. experiment. Entwickelungslehre der Wirbeltiere, Bd. I, Teil I, 1903. 



HUBER, G. CARL: The Development of the Albino Rat. Memoirs of the Wistar Institute, 

 No. 5, 1915. 



LILLIE, F. R.: The Development of the Chick. New York, 1908. 



MORGAN, T. H.: The Development of the Frog's Egg. New York, 1897. 



SOBOTTA, J.: Die Befruchtung u. Furchung des Eies der Maus. Arch. f. mik. Anat., 

 Bd. XLV, 1895. 



VAN BENEDEN, E.: Recherches sur les premiers stades du developpement du Murin 

 (Vespertilio murinus). Anat. Anz., Bd. XVI, 1899. 



WILSON, E. B.: The Cell in Development and Inheritance. 2d Ed., 1900. 



