PRODUCTION OF DOUBLE EMBRYOS 



201 



re-orlent the egg after the hair loop has attained a grip on the capsule. The 

 blastomerea can he separated without rupturing the fertilization (vitelline) mem- 

 brane . 



The loop should hold as a result of friction and the egg can he removed to an 

 appropriate #2 Stender for continued development and observation. However, very- 

 fine hair or individual fibers of silk can sometimes be looped twice, resulting in 

 ever better (friction) holding. The degree of constriction can be controlled with 

 practice. 



A second method but one which aims at complete separation of the blastomeres is 

 to remove the jelly capsule and separate the blastomeres (through the fertilization 

 membrane) by means of a cutting movement of the side of a glass needle. This can 

 be done without rupture of the membrane. Controls for this consist simply of eggs 

 deprived of their Jelly. 



OBSERVATIONS AMD TAHJLATION OF DATA: 



1. Make sketches of any changes in the superficial pigmentation of the inverted 

 eggs, as compared with the controls. Determine whether these changes are carried 

 over to the period of gastrulation. Sketch at periodic intervals. 



2. During neuLulation it should be possible to select those embryos which will, in 

 all probability, develop into double monsters. Keep accurate and periodic 

 records of developmental changes in specific eggs of this category. It is most 

 Important that any sequence of sketches represent the changes in a single egg. 



BEFfeRKNCES : 



Hadorn, E., 1957 " "Die entwicklungsphysiologische Auswirkung der disharmonischen Kern- 

 Plasma-Kombination beim Bastard-Merogon Triton palmatus x T. cristatus." Arch. f. 

 Ent. mech. 156:14-00. 



Harvey, E. B. , 19i4-0 - "A new method of producing twins, triplets, and quadruplets in 

 Arbacia punctulata, and their development." Biol. Bull. 78:202. 



Hinrichs, M. A. & I. J. Genther, 1951 - "Ultra-violet radiation and the production of 

 twins and double monsters." Physiol. Zool. l+:'+6l. 



Lynn, W. G. , I958 - "Conjoined twins and triplets in trout." Anat. Bee. 70:597- 



Mangold, 0., I92I - "Situs inversus bel Triton." Arch. f. Ent. mech. 1*8:505. 



Pasteels, J., 1955 - "Eecherches aur les facteurs Inltlaux de la morphogenese chez lea 

 amphibienes anoures. I. Kesultates de 1' experience de Schltze et leur interpreta- 

 tion." Arch. Biol. !+9:629. 



Penners, A. & W. Schleip, I928 - "Die Entwlcklung des Schultzeschen Doppelbildungen aus 

 dem Ei von Eana fusca." Zeit. f. Wiss, 150:506. (Also ibid. 151:1.) 



Schwind, J. L., 19l*2 - "Spontaneous twinning in the Amphibia." Am. Jour. Anat. 71:117' 



Spemann, H. & H. Falkanberg, I9I9 - "Ueber asymmetrische Entwlcklung und Situs Inversus 

 viscerum bel Zwillingen und Doppelbilungen. " Arch. f. Ent. mech. 14-5:571. 



Weasel, E;, I926 - "Experimentell erzeugte duplicltas cruclata bei Triton." Arch. f. Ent. 

 mech. 107:1+81, 



TAIL 



HEAD 



CHIMEflA - fusion of anterior 

 ends of Raiia plpiens embryos. 



HEAD 



