STATE GEOLOGIST. 51 



The length is 0.43 mm.; width .33 mm. in the average, though 

 €ggs were occasionally found of an elongated form, measuring .48, 

 .31 mm. The contents of the egg consist of spheres of greenish 

 plasma of various sizes and fat or oil drops. These oil globules are 

 not very numerous as compared with those of the summer eggs, 

 and likewise never attain the dominant size seen in the latter. 

 The various forms assumed by the plasma balls are perplexing but 

 frequently result from the action of external agents. The cleavage 

 stage was not seen, and if actual segmentation takes place, it 

 must be inconspicuous as would be expected from the large quan- 

 tity of yolk present. The differentiation of the blastoderm occurs 

 very early, perhaps in the ovary itself, and the result is a tolerably 

 uniform layer of prismatic cells. The egg now comes to a period 

 of repose after the blastoderm has produced a second external 

 envelope apparently by simple secretion. 



This envelope consists of a fine structureless membrane. The 

 egg, under ordinary circumstances, remains dormant during the 

 winter in this most favorable stage. The reason for which is evi- 

 dently the fact that the differentiation has proceeded to the extent 

 of producing the greatest number of protective layers without 

 materially increasing the complexity, and thus the sensitiveness, of 

 the organism. Under favorable circumstances the development 

 proceeds farther and near one pole appears a slight indenture of 

 the surface which grows deeper and seems to form a true invagina- 

 tion. This blastopore, if such it really be, remains for some time, 

 generally till the two '* scheitel " plates appear. These '' scheitel- 

 platfce " are formed by a simultaneous thickening and lengthening 

 of the cells of limited areas on opposite sides of the egg^ near the 

 opposite pole from that occupied by the blastopore. The '^scheitel- 

 platte" are situated at right angles to a plane perpendicular to the 

 blastopore. The nuclei of the cells of the "scheitelplatte" are 

 nearly .0208 mm. in diameter, while those of the other blastoderm 

 cells are about half that size. 



The egg remains a long time in this stage, while the following 

 stages are passed through quite rapidly till the embryo assumes its 

 nauplius form. The remainder of the development agrees, so far 

 as seen, quite fully with that of the summer eggs, to which we will 

 now return. 



The summer eggs vary greatly in size and number, but are 

 nearly as large as the winter eggs. The number is sometimes re- 

 duced to two or three or rises to as many as fifteen or even more. 

 In color the eggs also vary from green to brown. The fresh egg 



