CULTURING ISOLATED ANLAGEN 255 



DISCUSSION : 



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

 fragment 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 provided with an adequate culture medliim, it must supply its own energy for growth and 

 development, 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 

 because 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 

 determined, for Instance, to what extent the ecto- , meso- , and endoderm are related to 

 the development of the gills, which structure In the normal embiyo is composed of all 

 three germ layers. 



BEFERENCES : 



Baker, L. E., 1938 - "The secretion of iodine by thyroid glands cultivated In the Lind- 

 bergh pump." Sc, 88:'+T9. 

 Bautzmann, H. , 1929 - "Tiber bedeutungsfremde Selbstdlfferenzlerung aus Teilstucken des 



Amphibienkelme." Naturwiss. 17:8l8. 

 Bloom, W., 1957 - "Cellular differentiation and tissue culture." Physiol. Eev. 17:589. 

 Brachet, J. & Eapklne, 1959 " "Oxydation et reduction d'explantats dorsaux et ventraux d© 



Gastrulas ( Amphibien) . " Comp. rendu. Soc. Biol. 131:789. 

 Dorris, F., I938 - "Differentiation of the chick eye in vitro." Jour. Exp. Zool. 78:385- 



(See also 19^0: Pro. Soc. Exp. Biol. & Med. kk:266.) 

 Erdmann, W. , 1931 - "Uber das Selbstdifferenzlerungsvermogen von Amphibienkeimtellen 



bekannter prospektiver Bedeutung im Explantat." Arch. f. Ent. mech. I2k:666. 

 Esakl, S., 1929 - "A sure method for the elective staining of neuroflbrlllae in tissues 



cultivated in vitro." Ztschr. f. wlss. Mlkrosk. 1+6:569 (See also Comp. rendu. Soc. 



d. Anatom. 2li:225). 

 Fell, H. B. & E. Eoblson, I93O - "The development and phosphatase activity in vivo and in 



vitro of the mandibular skeletal tissue of the embryonic fowl." Bioch. Jour. 



21^:1905. 

 Filatow, D. , 1926 - "Uber die Entwicklung des Augenkeimes einlger Amphibien in vitro." 



Arch. f. Ent. mech. 107:575. 

 Fischer, I., I938 - "Uber die Dlfferenzlerung Melanophoren und Lipophoren in Extoderm- 



explantaten von Amblystoma." Arch. f. Exper. Zellforsch. 22:55. 

 Fostrect, G., 1959 - "Preliminary in vitro studies of melanophore principle activity of 



the pituitary gland." Proc. Soc. Exp. Biol. & Med. 1+0:502. 

 Goerttler, K. , I928 - "Die Bedeutung der ventralateralen mesodermbezirke fur die Herzen- 



anlage der Amphibienkelme." Verb. Anat. Ges. 57:132. 

 Hadorn, E., 1951+ - "Uber die Entwicklungsleistungen bastardmerogonischen Gewebe von 



Triton palmatus ( ) x Triton cristatus ( ) Im Ganzkeim und als Explantat in vitro." 



Arch. f. Ent. mech. 151:258. 

 Harrison, E. G., I828 - "On the status and significance of tissue culture." Arch. f. 



Zellforsch. 6:14-. 

 Hetherington, D. C. & J. S. Craig, 1959 - "Effect of frozen-dried plasma and frozen-dried 



embiyo Juice on tissue cultures." Proc. Soc. Exp. Biol. & Med. 1+2:851 

 Hitchcock, H. B., I959 - "The behavior of adult amphibian skin cultured in vivo and In 



vitro." Jour. Exp. Zool. 81:299. 

 Hogue, M. J., 1952 - "The reaction of tissue-culture cells to barium (x-ray) sulphate." 



Anat. Eec. 5'^:307. 

 Holtfreter, J., I958 - "Dlfferenzierungspotenzen isolierter Telle der Urodelengastrula. " 



Arch. f. Ent. mech. 158:522 (See also ibid 158:657). 



