ANDROGENESIS I83 



small amount of cytoplasm and yolk will he included, and this must be kept at a minimum. 

 Transfer the operated egg to a covered #2 Stender with fresh Urodele Growing Solution or 

 Spring Water and keep it at a constant temperature in the vicinity of 15° to 18°C. 



CARE OF MATERIAL : 



Operated eggs should he examined within several hours to determine whether they are 

 cleaving. Such eggs as seem to he developing, and show operation exudates, should he 

 isolated in #2 Stenders with the appropriate medium and should he kept at the cooler tem- 

 peratures within the normal range. Controls must be kept at the same temperatures and 

 under the same conditions of medium and space. 



OBSERVATIONS AND TABULATION OF DATA : 



There are two criteria for successful androgenetic operations. 



a. Delay in cleavage and early development . The first cleavage may be delsiyed as 

 much as k'^ minutes (at 22°C.) and development through neurulation will tend to 

 be delayed. After hatching, the embryo will manifest those characteristics 

 normally associated with experimentally induced haploidy such as in artificial 

 parthenogenesis. These include stunting, dorso-ventral thickening, dorsal 

 flexion of the head and tail, oedema, reduction of the gills, etc. (see photo- 

 graphs of abnormalities in development and haploid larva in section on Arti- 

 ficial Parthenogenesis). Make drawings of androgenetic embryos and tadpoles. 



b. Chromosome count which should be haploid . This can be determined in the neuru- 

 la stage either by sectioning and staining the material, or by making cover- 

 glass smears of neural crest cells (see Culturing Isolated Embryonic Cells) 

 and staining them with Harris' haematoxylin. Those tadpoles which survive for 

 10 days or more can have their tails clipped and examined (see Tall Tip Chromo- 

 some Technique) for chromosome figures, without killing the tadpole. 



