Fig. 187.—Diagrams to illustrate the method of development of the amnion. The embryo and the rest of the yolk are supposed to be seen in median longitudinal section; the head end is to the right. For convenience, the yolk-membrane (yk.m.) is represented at some distance from its contents. am, folds of amnion; am.c., amniotic cavity; em, embryo; yk, yolk; yk.st., yolk-stalk. (After Foster and Balfour.)
[18] I desire to acknowledge my indebtedness, in drawing up this section, to Prof. Lloyd Morgan’s Habit and Instinct (Arnold).
[19] Lloyd Morgan’s Habit and Instinct (Edward Arnold).
[20] Lloyd Morgan’s Habit and Instinct (Edward Arnold).
[21] Our Bird Friends (Cassell).
[22] The Natural History of Selborne.
[23] The Natural History of Selborne.
[24] A delightful account is given in the story of “Silverspot” (Thompson-Seton’s Wild Animals I Have Known).
[25] Latin, passer, a sparrow.
[26] The Cambridge Natural History, Vol. VIII. (Macmillan.)