158 A. S. PACKARD, JR., ON THE 



slightly enlarged) with small nuclei, dark in color, being seen with reflected light. They 

 were round, or irregularly hexagonal when crowded together (fig. 6, a, enlarged 130 diam- 

 eters). The interspaces were dark, of the same color as the nuclei, and appeared as if 

 forming a fine net work covering the egg. They were difficult to detect, owing to the great 

 opacity of the egg, but could be seen under a strong reflected light. In two days after 

 the fertilization of the eggs, this layer of nucleated cells disappeared. 



The surface of the yolk then became covered with rounded masses, becoming somewhat 

 hexagonal when crowded, and made up of yolk granules. This balled appearance was ob- 

 served a few days earlier in many of the eggs received from Mr. Lockwood, and can be 

 easily seen with the naked eye. These balls soon disappeared and the surface of the egg be- 

 came smooth again, and then the eggs presented the appearance noticed in the egg re- 

 ceived from New Jersey, described below and figured on PI. in, fig. 6, h, and 7. After a few 

 days the surfiice of the yolk became again as seen in the naturally impregnated eggs just 

 before the appearance of the germ, the transparent cells of the blastoderm being readily 

 seen with a ToUes triplet. 



While writing in my notes the preceding paragraph, an egg in which the blastodermic cells 

 were distinctly developed, appearing like Claparede's^ figure 1 (my fig. 6), went through 

 under my eyes the following change alluded to above. The original blastoderm cells disap- 

 peared from view, and the surface of the yolk was suddenly covered with white masses of 

 different shapes, but more or less angular. They seemed in the space of a few minutes 

 (not more than five or ten) to start out into view and suddenly become very distinct. 

 They were shining white, were easily seen with the naked eye, and were very irregular in 

 size, some masses being ten times as large as others. The surface of the yolk was now 

 roughened. The masses were made up of cells filled with granules. It seemed (though I 

 may be hereafter corrected in this opinion) as if these balls were due to a rapid multiplica- 

 tion of blastodermic cells, resulting from the subdivision of the primitive cells of the blas- 

 toderm (fig. 6). 



The artificially impregnated eggs did not develope farther, and remained in this state 

 from the 8th of June until the end of Jiily without materially changing. It will be desir- 

 able to repeat these observations and test their accuracy and I simply here place on 

 record what I saw at that time, subject to farther correction. But the egg covered with 

 the layer of pale nucleated cells, presented very much the same appearance as the blasto- 

 derm cells of the spiders as figured by Claparede ^ and what I observed in the eggs of 

 Pholcus, which Mr. J. H. Emerton, then engaged in studying the embryology of our spi- 

 ders, had the kindness to show me at the time of writing out these notes. They also ac- 

 cord with the blastodermic cells of Gammarus jluviatilis, in their earliest development, as 

 figured by Prof. E. Van Beneden, ^ and another species doubtfully referred to this last form 

 by Profs. Van Beneden and Bessels.* The formation of the blastoderm, then, if my observa- 

 tions are correct, exactly accords with that of the Arachnida, and the fresh water species 



1 Recherches sur revolution des Araignees, etc. ' Memoiie sur la Formation du Blastoderrae chez les Am- 



'^ Rechorclies sur I'fivolution des Araignees, 1862. PI. 1, phipodes, les Lerneens et les Copepodes, par Dr. Edouard 



figs. 1, 58, 59, 60. Van Beneden et Dr. Emil Bessels. Mem. Couronnes etMem. 



'Recherches sur la Composition et la Signification de des Savants Etrangers, Acad. Roy. des Sciences, etc., de 



I'CEuf. Mem. Couronne, Acad. Roy. de Belgique, Tom. 34, Belgique. Tom. 34, 1870. PI. 2, figs. 16, 17. 



1870, PI. 10, figs. 1-4. 



