THE GERM-RING IN THE EGG OF THE TOAD- 

 FISH (BATRACHUS TAU). 



LOUISE B. WALLACE. 



Smith College, Northampton, Mass. 



Since the Toad-fish has a number of characteristics peculiar 

 to itself, it is natural to expect that it would differ from the 

 ordinary teleost in its mode of development. The marked 

 resemblance of the egg to that of Elasmobranchs has already 

 been noted/ but the formation of the germ-ring has been left 

 an open question. My observations were made during the 

 summers of '95 and '96, under the direction of Dr. Whitman, 

 at the Marine Biological Laboratory, Woods Holl, Mass. 



It gives me great pleasure to express my indebtedness also 

 to Dr. Cornelia M. Clapp for many helpful courtesies. 



After the middle of June most of the material found in nests 

 in Buzzards Bay was in an advanced condition, and it was neces- 

 sary to resort to artificial fertilization. Eggs were fertilized 

 by hundreds, covered with sea-water in shallow dishes, and 

 studied from the earliest stages. The egg of Batrachus is 5 

 mm. in diameter, being much distended with yolk, and is, when 

 deposited, attached to some foreign body by means of an 

 adhesive disc. The blastoderm, in encompassing the yolk, is 

 spread out into a cap of extreme tenuity, requiring delicate 

 treatment. After repeated effort the paraffin method was 

 given up and good results were obtained by use of the cel- 

 loidin method with either Hermann's fluid or Flemming's fluid 

 as fixing reagents. 



Not until the fourth or fifth day after fertilization does a 

 distinct axial thickening appear, with oftentimes a slight, mar- 

 ginal notch at the embryonic pole, and there is no marginal 

 thickening around most of the blastoderm (PI. II, Fig. 6). A 

 median, longitudinal section is shown in PI. Ill, Fig. i. In 



1 Cornelia M. Clapp, " Some Points on the Development of the Toad-fish 

 (Batrachus tau)." Jotirn. of Morpli., vol. v, No. 3. 



