REVIEW 311 



this extra oxygen, the pulmonary circulation becomes active, the 

 embryonic circulation ceases, and the allantois shrivels up, since 

 its use is no longer needed. The chick now has room to move its 

 head/and it begins to break the shell by dealing blow after blow with 

 its beak upon one spot on 

 the inside until the shell 

 is punctured (Fig. 150). 

 This performance is re- 

 peated, in a new place 

 each time, until the shell is 

 broken all around about 

 one-third of the distance 

 from the large end. All 



the Chick nOW has tO do FIG. 150.-Hatching time. One egg completely 



to get Ollt from the Shell IS Pipped ready for the final effort of the chick; the 



^f. V^,^ r,+^ f other chick is resting after the effort. (Photo by 



tO lOrCe these two parts Of Hearson, Ltd.) 



the shell apart by pressing 



its feet against the small end and its head against the large one, 

 which it throws off. It takes the chick some time to dry off and 

 get the use of its legs, and usually from one to three hours elapse 

 after hatching before it becomes very active. 



REVIEW. 



1. Why need the fowl's reproductive system be so complicated? 



2. The hen's reproductive system is composed of what two parts? 



3. Where is the ovary located and what is its work? 



4. Describe the appearance of the ovary and yolk sacs. 



5. Describe the maturity of an ovum and its entrance into the oviduct. 



6. What is the oviduct? What are its uses? 



7. Where is the egg fertilized? 



8. Describe the changes in the egg during its passage through the oviduct. 



9. Enumerate the parts of a completed egg, and give the use of each part. 



10. Give the approximate composition of the whole egg, with and without 



the shell. 



11. Mention the types of malformed eggs, and give the cause of each. 



12. Discuss the fertile and infertile egg. 



13. Describe the development of the embryo which takes place before the egg 



is laid. 



14. Describe the first day's development during incubation. 



15. Describe the appearance of the embryo when thirty-six hours old. 



16. Describe the appearance of the embryo when seventy-two hours old. 



17. Give subsequent development from third day to hatching time. 



18. Describe the process of hatching. 



Reference. Reproductive Organs of the Hen, by D. F. Laurie, South 

 Australia Department of Agriculture Bulletin 72. 



