EXPERIMENTAL FISH EMBRYOLOGY 



391 



c. The Culturing of Fish Explants in Vitro 



This type of investigation, so readily achieved with amphibian and even with chick ma- 

 terial, proves satisfactory but to a lesser degree with fish embryonic parts. Oppen- 

 heimer (1938) cultured parts of Epiplatys fasciolatus in a modified Ringer's for from 4 

 to 7 days and secured tail-like differentiation without histogenesis. (See also Trinkhaus 

 and Drake 1956) 



Figs. 1 to 7. The types of differentiation attained in isolation blastoderms which have not 

 gastrulated. These are hyperblastulae, masses of cells generally differentiating only a hollow 

 vesicle whose wall represents the ectodermal portion of the yolk-sac epithelium. The stage 

 at which the blastoderms were removed from the yolk, and the number of days they sur\'ived 

 before preservation, are indicated in parentheses. Cell walls are represented only in Fig. 1. 

 Fig. 



Fig- 



1. 



Hyperblastula in which the non-differentiated embryonic cells form a compact mass 

 in the center of the vesicle. (16-celled; 4 days. ) 



Hyperblastula in which the non-differentiated mass of cells is continuous with the 

 vesicle epithelium at one region only and surrounded elsewhere by a columnar epi- 

 thelium. (32 -celled; 3 days. ) 



Fig. 3. Explant whose differentiated cells are joined to the vesicle epithelium by a mesen- 

 chymatous network. (8-celled; 4 days. ) 



Fig. 4. Explant in which the cellular arrangement suggests the occurrence of irregular cell 

 movements. Except for the formation of columnar epithelium no histogenic 

 changes have taken place. The cell movements were not those of gastrulation. 

 (16-celIed; 3-3/4 days.) 



Fig. 5. Hyperblastula containing two different types of cells, one non-differentiated, the 

 other with denser nuclei and more heavily staining cytoplasm (NV). These prob- 

 ably present cells which have commenced self-differentiation of nervous tissue 

 without the inductive stimuli of gastrulation. (64- to 128-celled; 3-3/4 days. ) 



Fig. 6. Hyperblastula in which one group of cells has the dense nuclei characteristic of 

 nervous tissue (NV), while another group (N) is surrounded by a hea\'y sheath 

 similar to that normally surrounding the notochord. These cell groups are large 

 spherical masses, surrounded by homogeneously arranged non-differentiated cells; 

 their differentiation has been independent. (2-celled; 3 days. ) 



Fig. 7. Hyperblastula in which a small group of cells, probably epidermal in origin, have 

 begun to self-differentiate nervous tissue (NV). (8-celled; 6 days. ) 



(From Oppenheimer 1939: Jour. Exp. Zool. 72:245) 



Procedure: 



1. Insure complete asepsis, autoclaving the media and sterilizing all instru- 

 ments. and glassware. Culturing can be in deep depression slides, or in 

 covered and sealed §1 Slenders. 



