222 CULTURING ISOLATED ANIACEN 



m^ V ^^ %^' 



u^ 



% 



Progressive development of gill anlogen 

 of Amblystoma in isolation. 



(From Moser, 1940: Jour. 

 Morph. 66:261) 



DISCUSSION: 



This type of experiment simply tests the self-differentiating capacity of a germinal frag- 

 ment and is to be compared with the transplantation of the same fragment to a living host, 

 particularly to heterotopic positions. In the isolated condition the explant must be pro- 

 vided with an adequate culture medium, it must supply its own energy for growth and de- 

 velopment, and if it is to differentiate it must have acquired some pattern influence before 

 excision. It is this pattern which is the interest of this experiment. 



No synthetic medium has yet been devised which is perfect enough to satisfy living cells 

 so that they can differentiate normally for an indefinite period. In the younger explants 

 there is apt to be greater survival because the cells possess yolk reserves upon which 

 they may call. Nevertheless, morphogenetic differentiation in such explants is rare be- 

 cause they have not received inductive influences from their surrounding areas, but cel- 

 lular and even histological differentiations in such early explants may be seen. 



The most instructive aspect of this exercise will relate to the determination of the value 

 of the various germ layers in the differentiation of specific organs. It should be deter- 

 mined, for instance, to what extent the ecto-, meso-, and endoderm are related to the 

 development of the gills, which structure in the normal embryo is composed of all three 

 germ layers. 



REFERENCES 



BAKER, L. E. , 1938 - "The secretion of iodine by thyroid glands cultivated in the Lindbergh pump. " Sc. 88:479. (See also 



Science 83:605, 1936). 

 BAUTZMANN, H. , 1929 - "Uber debeutungsfremde Selbstdifferenzierung aus Teilstucken dcs Amphibienkeime." Noturwiss. 17:818. 

 BLOOM, W., 1937 - "Cellular differentiation and tissue culture. " Physiol. Rev. 17:589. 

 BRACKET, J. G RAPKINE, 1939 - "Oxydation et reduction d'cxplantots dorsaux et ventraux de Gastrulas (Amphibien). " Comp. 



rendu. Soc. Biol. 131:789. 

 DORRIS, F. , 1938 - "Differentiation of the chick eye in vitro. " Jour. Exp. Zool. 78:385. (Sec also 1940: Pro. Soc. Exp. Biol. 



CMcd. 44:286.) 

 ERDMANN, W. , 1931 - "Uber das Selbstdiffereniierungsvcrmogen von Amphibienkeimteilen bekannter prospcktiver Bedeutiing 



im Explantat. " Arch. f. Ent. mech. 124:666. 

 ESAKI, S. , 1929 - "A sure method for the elective staining of neurofibrillae in tissues cultivated in vitro. " Ztschr. f. wiss. 



Mikrosk. 46:369 (See also Comp. rendu. Soc. d. Anatom. 24:223). 

 FELL, H. B. C R. ROBISON, 1930 - "The development and phosphatase activity in vivo and in vitro of the mandibular skeletal 



tissue of the embryonic fowl. " Bioch. Jour. 24:1905. 



