EXPERIMENTAL FISH EMBRYOLOGY 



i^l5 



DISCUSSION : 



The foregoing sections on Fish indicate that this Class of Vertebrates Is coming in- 

 to its own in the field of Experimental Emhryology, Most of the procedures outlined are 

 of an operational nature. 



There are also the studies on hyhridlzation; on environmentally Induced teratologies 

 ( Stockard, 1921); on the effect of x-lrradiation of one of the gametes (Solfcerg, I958); on 

 the physiological response of the embryo to changes in the environment (V'aterman, 19^+0 and 

 the various Japanese workers with Oryzias). There is an ever increasing amount of work of 

 a cytological and cytochemical nature, all of which should be Included in an exhaustive 

 treatise on experimental embryology of fish- 



The teratologlcal forms of fish embryos proiiuced bj Irradiating, germ cells. No. 1 

 represents a control embryo 4 days after fertilization. No. 2 shows slight reductions In 

 the anterior and posterior regions. The succeeding stages (3, 4 and 5) sliow greater re- 

 ductions of head and tall. Other parts are entirely lacking in these embryos. Deformi- 

 ties of the heart are shown In drawings to the right of each emoryo. Embryos deformed as 

 much as No. 5 often do not develop a Iieart. The heart deformities consist c)ilerii of an 

 elongation, and Improper formation ol t.ie chambers, usually associated with an edema of 

 the pericardial cavity. 



(FromSolberg I958: Jour. Exp. Zool. 28:'J-17) 



The fish are rapidly becoming a contestant for attention along with the amphibia. 

 Possibly the work of Oppenheimer (1959) cam be cited as a bridge between these two classes 

 of vertebrates, for she found tliat a large variety of fish anlagen differentiated quite 

 normally when grafted into the amphibian hosts and that "fish epidermis and cartilage have 

 been found morphologically continuous with coniparable structures formed by amphibian cells 

 in grafts," and "the fish grafts are occasionally seemirigly Innervated by nerves originat- 

 ing from the amphibian cranial ganglia; it is not known whether the apparent innervation 

 is a functional one." (Jour. Sxp. Zool. 80:592) 



