Outlines of comparative physiology touching the structure and development of the races of animals, living and extinct : for the use of schools and colleges . «, a _,. , , ripe yolk within its calyx or cup, the cicatrice disposed aroundof which, b, b, is seen as a transverse non-vascu-lar streak ; c, c, smaller yolks, with the vascularrete of their cups and their cicatrices; d, acalyx empty, the part having given way alongthe line of the cicatrice—smaller yolks (e) areenveloped by calices so transparent that the ci- ls a consequence orcatricula is seen through them. the rotatory motion upon its
Outlines of comparative physiology touching the structure and development of the races of animals, living and extinct : for the use of schools and colleges . «, a _,. , , ripe yolk within its calyx or cup, the cicatrice disposed aroundof which, b, b, is seen as a transverse non-vascu-lar streak ; c, c, smaller yolks, with the vascularrete of their cups and their cicatrices; d, acalyx empty, the part having given way alongthe line of the cicatrice—smaller yolks (e) areenveloped by calices so transparent that the ci- ls a consequence orcatricula is seen through them. the rotatory motion upon its axis which the ovum receives in the oviduct, and of the setting of thealbumen. The lower part of the oviduct is dilated into areceptacle for the egg, and here are added the membrane ofthe shell, and finally the shell itself, the milky calcareousfluid secreted by this part being precipitated upon the egg incrystals, which are at first isolated, but very soon run togetherand cohere. The egg remains over twenty-four hours in thereceptacle. The germ at the firnt entrance of the egg into theoviduct has already assumed the appearance proper to it at any. a yolk in the differentlayers but just de-scribed. The forma-tion of the chalazEe DEVELOPMENT OF THE CHICK—FIRST PERIOD. 295 period anterior to the commencement of incubation, the ger-minal vesicle having burst; the upper disciform layers of thegerm and germinal cumulus only separate more and the egg is thus perfected, it is forced rapidly throughthe cloaca. In other birds, it is here perhaps that the eggreceives, in part at least, the beautiful colours, red, green, yel-low, brown, &c., in various shades, which are so frequentlymet with, and which appear to be so many tints of the colour-ing matter of the blood chemically altered. EARLIEST PERIOD IN THE DEVELOPMENT OF THE CHICK,FROM THE FIRST APPEARANCE OF THE EMBRYO TO THEFIRST TRACES OF CIRCULATION. [§ 482. The first period in the development comprehendsabout two
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectzoology, bookyear1870
