272 



,0 



ESOPHAGUS 



P 



OLFACTORY PIT 



TELENCEPHALON 



=& 



EMBRYOLOGY 



OTOCYST 



MESONEPHROS 



the similarity to Figure 97, a diagram of the five primary divisions of the 

 chick brain. The sense organs, such as the nasal pits, follow the same pattern 

 of development as in lower vertebrates. Figure 178 shows the invagination 

 of the ectoderm to form the olfactory pit. The neuroblasts in the lining of 

 this pit grow into the telencephalon and form the first cranial nerve. Figures 

 179 and 180 are photographs through the eye and ear region of the pig 

 embryo. The development of these structures is very similar to the develop- 

 ment of the eye and ear in the chick embryo (Chap. 11). During the de 

 velopment of the digestive system we find a striking similarity in the pharyn- 



