248 



PARABIOSIS AND TELOBIOSIS 



area of ectoderm, mesoderm, and some yolk from each of the embryos. Quickly 

 maneuver the embryos together into the Permoplast depression, approximately 

 their wounded areas. Build up the Permoplast around them in such a manner that 

 they cannot move, but do not distort either embryo with excessive pressure. If the 

 cilia are active, an adequate block in front of the pair will impede them sufficiently. 



Parabiosis means lateral fusion. This may be side-to-side; back-to-back; belly-to- 

 belly; or a combination of these. The side-to-side fusion is generally the best be- 

 cause the larvae are permitted to move about and to feed in quite a normal manner. 

 The lateral fusion of three embryos has been achieved. 



TELOBIOSIS 



The technique of terminal fusion is identical with that above except that the Permo- 

 plast depression is long and narrow, and the injured areas are terminal rather than 

 lateral. Simply cut off the tip end of the heads, tails, or combinations, using sharp 

 and sterile scalpel or scissors. Bring the cut surfaces together and hold them ap- 

 proximated until healed. The relations may be head to head; tail to tail; or head to 

 tail. Also, one of the embryos can be inverted. 



OBSERVATIONS AND TABULATION OF DATA: 



1. Determine the growth rate of paired embryos as compared with the controls. 



2. Is there any evidence of dominance of one member of the pair over the other? 



3. How large a discrepancy in stages can be used for successful parabiosis? Discrep- 

 ancy in species? (See section on "Transplantations".) 



The data should be recorded in the form of photographs or drawings, and preserved spec- 

 imens which survive to the later stages. 



FUSED «r STAGE 16 



OIEO iNO PHOTOGRAPHED 

 AT 73 DAYS OF AGE 



Rana pipiens tadpoles 

 in parabiosis, fused at 

 stage 16 photographed 

 at stage 24. 



PARABIOSIS IN METAMORPHOSED FROGS 

 (RANA PIPIENS) 



Tulipan C Schreiber, 1942 



