[3] KETAKDING DKVELOPMEXT OF SHAD EGGS. 797 



Grace, Md., in 1880, The cells of the germiual disk became browDisb, tbe 

 cleavage furrows obliterated, the disk tended to spread out and become 

 larger across. These phenomena indicated stagnation of development 

 and death. The second series of experiments, conducted by what is 

 known as the " dry method," in a refrigerator box provided with canton 

 flannel trays, devised by Mr. F. N. Clark especially for these experi- 

 ments, gave better results. We found that the ova merely kept damp 

 on the trays in an air temperature of 52° api)eared to develop quite 

 normally, the only serious drawback being the rapid and more or less 

 fatal development of fungus, the mycelium of which would soon grow 

 over the eggs, penetrate the membranes, cause them to collapse, trans- 

 form the protoplasm of the vitellus into fungus protox>lasm, and kill 

 the ova. 



The following abstract from my note-book, recording what was ob- 

 served in watching the results obtained from a trial of Mr. Clark's 

 apparatus, speaks for itself, though it would facilitate the comprehen- 

 sion of the matter if a series of explanatory figures could be introduced : 



" Eggs taken June 8 and put into refrigerator at 9 o'clock p. m. ; exam- 

 ined June 9 at 9 o'clock a. m. ; exposed for 12 hours to a temperature 

 ranging from 54° to 00° F. Cleavage has advanced to the morula stage ; 

 i. e., the germinal portion of the egg is still discoidal, lies on one side 

 of the vitellus or yelk, and has not advanced beyond the condition ordi- 

 narily reached in three hours with the temperature 72° F. 



" Same lot, June 9, 2.30 p. m., advanced but a little be.yond the stage 

 just described above ; the germinal disk still maintains its character- 

 istics ; development normal ; temi)erature 54° F. 



'' Same lot^ June 10, examined at 9.30 a. m. ; segmentation cavity de- 

 veloped and blastoderm forming ; incipient embryo making its appear- 

 ance at one side. The blastoderm, however, does not yet cover more 

 than half of the upper hemisphere of the vitellus, a condition ordinarily 

 attained in six hours Vv-ith the temperature of the water at 72° F. 

 Temperature in refrigerator box now ranging from 52° to 54° F. Eggs 

 of the same age, 3GJ hours, in a hatching-jar, have the vitellus com- 

 pletely inclosed by the blastoderm, the embryo formed, wjth eyes, ears, 

 and brain distinguishable, and the tail is budding out as a small, 

 rounded knob at the posterior end of the embryonic axis, which curves 

 around one side and now extends from one pole of the egg to the other, 

 embracing an arc of 180°. 



" Same lot, in refrigerator, examined June 10, at 8.30 p. m., or nearly 

 forty-eight hours after impregnation, shows that the blastoderm has 

 grown down half way over the vit.41us, like a hemispherical cap ; the 

 keel or carina has been developed. Temperature 53° F. in refrigerator 

 all day. Eggs in a cone of the same age, temperature of the water 65° 

 F., have the embryos well advanced, with the tail free and as long as 

 the portion of the body still in contact with the yelk, but the natatory 

 fold is not developed. 



