l6it 



CHEMICAL EFFECT ON 'GROWTH 4 DIFFERENTIATION 



5. Place 25 gastrulae in each of the finger bowls, and record the exact time and 



stage. 

 k. After 2k hours, pour off all experimental media and wash twice with control 



medium. Finally place the embryos in 50 cc. of the control medium. 



5. Allow the embryos to develop under controlled conditions to Anura stage #22 or 

 Urodela stage #^+0 (swimming), examine, and fix in 10^ formaldehyde. (Various 

 degrees of exo-gastrulae, monorhyny and cyclopia will be found.) 



************* 



6. The long exposure of 2k hours may prove to be too drastic for the species used, 

 as evidenced by the mortality and teratoligies of the experimental embryos. For 

 those solutions which produce such drastic effects, reduce the exposure to 6 or 

 even to 2 hours. 



DISCUSSION : 



Experiments in animalization and vegetalization have been standardized for the 

 Echinodermata but Adelmann, Lehmann, and Hall have each demonstrated that Lithium Chloride 

 will effect the medium strip of organizer material of Amphibia resulting in exo-gastrulae, 

 which have faulty inductions (in consequence). A large variety of substances interfere 

 with gastrulation, but Lithium Chloride seems most satisfactory in the uniformity and 

 reproducibility of its effects. 



Hall (19^+2) has shown that even with Lithium Chloride the results will depend upon a 

 number of factors such as (a) concentration of Lithium (b) duration of exposure to the 

 salt (c) phase of development of the embryo (d) temperature of medium (e) presence of 

 other salts. The effect on differentiation is due to upsetting the delicately balanced 

 developmental factors that are so important at the time of gastrulation, and the manifes- 

 tations relate largely to the head and the tail organizers. By applying the Lithium 

 Chloride for 6 hour exposures at different stages of development, Lehmann has determined 

 a shift in susceptibility with progressive development. The effects are lessened at the 

 lower temperatures, and in the presence of calcium and the salts of the control medium. 



Histological examination is desirable but not necessaiy to identify the various types 

 of developmental abnormalities. Material may be fixed in Bouin's for sectioning, or in 

 10^ formaldehyde for dissection. 



-N_-t) 



CYCLOPIA IN AMBLYSTOMA PUNCTATUM EMBRYOS 



Figs. la. embryo ol' 32 somites; lb - embryo of 8 mm.: 

 Ic - embryo (In Mg) of about 12 mm. 



Figs. 2a. eraorj'o of 31 somites; 2b - embryo of 5.5 mm.; 

 and 2c - embryo of about 9.5 mm. 



An but Ic from lithium treatment. The "1" group ex- 



liiblt cyclopia complete and the "2" group exhibit 



cyclopia incomplete. 



From Adelmann 195'^: Jour. Exp. Zool. 67:21? 



