EXPERIMENTAL CHICK EMBRYOLOGY 



435 



THE DIFFERENTIATION OF CHICK EXPLANTS ON VARIOUS TYPES OF MEDIA 



SALINE- 

 AGAR 



SALINE- 

 AGAR 



YOLK- 

 ALBUMCN 



(EMTIRE E&C 

 CONTtMTS) 



SALINE - 

 AGAR 



+ 



YOLK 



EXTRACT 



(TRACE OF 

 ALeUMEN) 



g:^ 



GENERALIZED RESULTS 



lOt HOURS LATER 20; HOURS LATER 



NON- 

 BUFFERED 

 SALINE- 

 AGAR 



+ 



PURE YOLK 



EXTRACT 



|no albumen] 



YOLK 

 EXTRACT 



(TRACE OF 

 albumen) 



8UFFERE0 



SAUNE- 



AGAR 



+ 



PURE YOLK 



EXTRACT 



NO ALBUMEN) 



SALINE- 

 AG A R 



+ 



PURE 



ALBUMEN 



EXTRACT 



[NO yolk) 



(T) 



101 HOURS LATER 



20 « HOURS LATCR 



Development on various media. The sketches 

 are based on camera luclda drawings of the 

 living explants. All are drawn approxi- 

 mately to the same scale. The numbers in 

 each block refer to the number of explants. 



i.e., 20 + hours after explantation. 

 Only the albumen which adheres to the 

 yolk after the ordinary method of 

 separating the 2. The yolk was not 

 washed. 



From Spratt 19^*7: Jour. Exp. Zool. 106:5l4-5. 



Cuts to "be made : (See figure, below) 



a. Tranaversely (I.e., at right angles to the embryonic 



axis) about 0.2 to 0.7 mm. posterior to the primitive 



pit, using both halves. 

 h. Transversely through the primitive pit level, using 



both anterior and posterior halves. 



c. Transversely anterior to the primitive pit (i.e., 

 through the early notochord) and simultaneously through 

 the middle of the primitive streak. This gives three 

 pieces of blastoderm, each potentially very different. 



d. Use also whole blastoderms. 



Procedure for culturing : 



(1) Transfer the embryo, or parts, to be cultivated by means of a wide-mouthed 

 pipette to the surface of a culture medium, orient as desired, and flatten it 

 out by sucking away all excess superficial medium with a fine pipette. The 

 embryo (or part) should float on a few drops (2 cc. ) of culture medium. 



(2) Cover the Petri dish and return it carefully to the incubator. 



