I02 NEW YORK STATE MUSEUM 



most to the middle of the embryo and from its anterior third to its 

 posterior fourth. The anterior extremity of the embryo is charac- 

 terized by irregular series of moderately large cells in the germ 

 plasm. February 26. the median mesodermal tissue was crowded 

 still further to one side by the darker ectoderm which now extends 

 to the middle of the embryo and appears to have elongated some- 

 what. Both extremities of the embryo have retracted a little from 

 the tip of the amniotic sac and are occupied by irregular series of 

 large cells. The following day the mesoderm was crowded still 

 further to one side by the darker ectoderm. At the anterior ex- 

 tremity of the embryo there was a mass of rather dark, fine-celled 

 tissue, possibly the corpus luteum and apparently separating by 

 fission, while the greater portion appears to be composed of globu- 

 lar, highly refractive cells grouped much as at the posterior ex- 

 tremity, which latter is narrowly margined by rather large, highly 

 refractive, indistinctly grouped cells, one or more being unusually 

 large. February 4th there was a distinct clear space in each ex- 

 tremity of the amniotic sac. The anterior extremity of the em- 

 bryo is distinctly lobed, the broader, less produced portion capped 

 with a mass of large, refractive cells, the small protuberant lobe 

 composed of fine tissue. The posterior extremity of the embryo is 

 distinctly bilobed. Unfortunately the numerous changes observed 

 in this embryo from this point on at least appear to be abnormal, 

 since the embryo disintegrated February 9th, though pulsations in 

 the mother larva continued normally till the 15th. 



A very interesting embryo was discovered in larva Y February 

 6th. The embryo extended from the seventh to the eighth ab- 

 dominal segments and had a length equal to nearly twice the dia- 

 meter of the mother larva. It was narrowly elliptical, with a 

 length approximately three times its diameter. The polar cells, 

 though visible, were not so conspicuous as in the younger embryo 

 illustrated on plate 30, figures 2 and 3. This embryo is composed 

 of nearly uniformly developed, rather transparent, semicuboidal, 

 ectodermal cells. At the anterior extremity there was a slight 

 thickening, apparently the much reduced cells of the corpus luteum. 

 The median portion was occupied by a rather broad streak of 

 dark, granular cells bordered on either side, including the ex- 

 tremities, by lighter, smaller-celled tissue. The mother larva was 

 alive, as evidenced by distinct pulsations. The following day a 

 distinct though small cap of cells was observed at the anterior 

 extremity of the embryo. At the posterior third of the embryo 



