OUTLINE FOR LABORATORY STUDY OF THE CHICK 339 



In a study of the Wolffian duct determine just how far anteriorly 

 and how far posteriorly it extends. Note whether it empties into 

 the cloaca. 



Each tube beginning in a blind extremity is later dilated. It has 

 a thin wall, and is situated near the median portion of the Wolffian 

 body. The tubule proper passing transversely, opens into the duct. 

 The upper wall of the thin-walled part is invaginated by a mass of 

 mesenchyme that receives a small vessel from the dorsal aorta. The 

 Malpighian corpuscle, consisting of a glomerule and Bowman's cap- 

 sule, is thus established. In the study of the four days old chick 

 note the further development of these parts. 



In a study of a chick four days, or ninety-six hours old, note to 

 what extent the yolk is covered by the blastoderm. It will be noted 

 that the embryo lies in the extra-embryonic cavity. This cavity is 

 bounded above by the chorion and below by the splanchnopleure. 

 In removing the amnion from the embryo, note the relation to the 

 somatic umbilicus. Note the relation of the splanchnic umbilicus 

 to the splanchno-pleure. What relation has the allantois to the 

 above? 



In examining the head, locate the cerebral hemispheres, and note 

 their development. Locate the pineal gland. Note changes in the 

 olfactory pit and the eye. Locate the lens and the choroid fissure. 

 Note that the maxillary process of the mandibular arch lies beneath 

 the eye and behind the olfactory pits. Note the otocyst and the 

 relations of the other arches to the above structures. 



In a study of the trunk, note the tail, the allantois, Wolffian 

 ridges, the heart, and the condition and the position of the rudi- 

 mentary limbs. 



Make drawing of embryo from the side view. Carefully cut off 

 the head immediately behind the last visceral arch, and study and 

 draw the structures observed on the ventral side. Note the maxil- 

 lary processes, the mandibular and the hyoid arch, the nasal pits, 

 and the fronto-nasal process, which is just beginning its development. 



In a study of transverse sections observe from your drawing at 

 what level the section is made. Study and draw a section made 

 through the region of the anterior limbs. Note the spinal ganglion, 

 the muscle plate, or myotome, the condensation of mesenchyme 

 around the notochord, the pancreas, the liver, and the intestine; 

 and note the distribution of the mesenchyme. Note the ventral 

 roots of the spinal nerves, and the neuroblasts in the spinal cord. 



