460 PRACTICAL DIRECTIONS. [APF. 



plasmic processes ; and in. the later stages to the 

 breaking np of these masses into blood corpuscles 

 and the conversion of the protoplasmic processes 

 into capillaries, with cellular walls. 



Blastoderms treated in the following ways may 

 be used to corroborate the observations made on the 

 fresh ones. 



With gold chloride. 



Immerse the blastoderm in gold chloride (-5 p.c.) 

 for one minute and then wash with distilled water 

 and mount in glycerine and examine. 



By this method of preparation, the nuclei and 

 protoplasmic processes are rendered more distinct, 

 without the whole being rendered too opaque for 

 observation. 



The blastoderm after the application of the gold 

 chloride should become a pale straw colour; if it 

 becomes in the least purple, the reagent has been 

 applied for too long a time. 



With potassium bichromate. 

 Immerse iu a 1 p.c. solution for one day and then 

 mount in glycerine. 



With osmic acid. 



Immerse in a '5 jd.c. solution for half an hour and 

 then in absolute alcohol for a day, and finally mount 

 in glycerine. 



Practical directions for obtaining and studying 



MAMMALIAN EmBRYOS. 



XI. Animals and breeding. 



For class work the Rabbit is the most convenient 

 animal from which to obtain embryos, it will breed 



