Emerton.J 394 [December 20, 



tween July 28th and Aug. 3d, laid their eggs and were found carry- 

 ing them bound together in a mass in the usual manner. 



In eggs examined within four hours after they were laid, the vitel- 

 lus was spherical and its surface covered with polygonal cells (PL II. 

 Fig. 1) filled uniformly with granules but showing no nuclei. Cells 

 with transparent nuclei soon appeared here and there (Fig. 2), and 

 within twenty-four hours covered the whole surface of the vitellus, 

 (Fig.3), which had meanwhile diminished in size and become some- 

 what flattened (Fig. 4) . One half was whiter and more opaque than 

 the other, and always turned upward, in whatever position the egg 

 might be placed. 



On the second day (July 31), a distinct white 'spot appeared a little 

 way from the centre of the upper side of the vitellus and slightly 

 elevated above its surface, the cumulus primatif of Claparede (Fig. 4). 

 From this extended a pear-shaped appendage which, at 4 P. M., Aug. 

 1, reached to the margin of the opaque upper half of the vitellus. 

 (Figs. 5 and 6). At the same time, beginning at the cumulus, the 

 whole surface became whiter except a strip on each side of the pear- 

 shaped appendage (Figs. 5 and 6). When the latter had reached its 

 full length its peduncle gradually became narrower and finally dis- 

 appeared entirely, while the central portion of the cumulus became 

 divided lengthwise by a transparent band, which widened toward the 

 point where the appendage began (Fig. 7). 



At 7 P.M., Aug. 1, the first traces of the segments of the body ap- 

 peared (Fig. 7) as four white stripes extending from the cumulus on 

 each side and finally meeting on the ventral surface, where two 

 more segments, one at each end, could be distinguished. These six 

 segments, which at first nearly encircled the embryo (Figs. 8 and 9)> 

 gradually separated on the dorsal surface until they extended only 

 half round it at 7 P. M., Aug. 2, and at the ends of each segment ap- 

 peared the rudiments of limbs which continued to approach toward 

 the ventral portion of the embryo (Fig. 10). At this stage the whole 

 embryo was barrel-shaped, and the head and abdomen were indicated 

 only by undefined whiter portions at each end (Fig 10). 



Aug. 3 the whole body became shorter and the limbs were about 

 half the diameter of the egg apart on the ventral side. The head 

 was distinctly outlined and the post-abdomen projected from the op- 

 posite end of the body (Figs. 11 and 12). Two segments of the ab- 

 domen had formed between the thoracic segments and the post-ab- 

 domen. At this stage first appeared a transparent band extending 



