INCUBATION 



i6r 



the blastoderm and gradually distribute themselves 

 over the whole of the yolk. 



At the end of i8 hours' incubation the head of the 

 future chick, with the eyes enormously developed, 

 and the spinal column, are plainly discernible under 

 the microscope. After 40 hours there is a complete 

 blood circulation, the heart is formed and beating 

 has commenced, and the blood vessels have spread 



EGG-TURNING CABINET 



Series of rollers over which canvas Is stretched. Each 

 compartment tray removable with false bottom, a, which slips 

 between canvas and tray frame. A, shows cabinet complete; 

 B, detail construction. 



themselves over a considerable portion of the upper 

 yolk. These are of a dual character; some are 

 arteries, taking blood away from the embryo, some 

 are veins bringing the blood back again. The heart 

 commences pulsating about the second or third day. 

 When the blood, circulation commences, the 

 necessity for another organ which has been de- 

 veloping next to the shell arises. There is another 



