40 



IÏASHFOIïI) PK VN'. 



In Fig. A., is shown an early stage. The egg was collected at the 

 time of deposition. There are few blastomeres and the radial pattern of 

 the marginal furrows is well marked. The germinal disc is seen at the 

 top of the figure. A somewhat similar stage is shown, Fig. B., from the 

 region near the vegetal pole. The germ disc is situated on the side away 

 from the observer: its position, however, is indicated by dots, as if shown 

 through the egg. The present specimen is an interesting one since it 

 shows one of the few cases in which I was able to satisfy myself that the 

 furrows could sometimes be traced well down toward the vegetal pole, in 

 fact that one or two of them actually traverse it. This stage well 

 illustrates the flattening of the groove-like ends of the cleavage lines. A 

 later stage, Fig. C, shows a greater number of meridional and marginal 

 cleavages. The germinal disc appears at the lower left hand side of the 

 figure In Fig. D., a lateral view is given of an egg somewhat similar 

 to the foregoing. The specimen is noteworthy in as much as the radial 

 (meridional) lines pass quite uniformly as far as the region of the equator 

 of the egg. More irregular in this regard is the egg shown in Fig. E. 

 In this several of the lines pass further towards the vegetal pole than 

 their fellows. In the egg shown in Fig. F., the meridional furrows pass 

 still further toward the vegetal pole. 



In Fig. Gr. is pictured the animal pole of an egg somewhat finely 

 subdivided by cleavage lines. In Fig. H., a stage of gastrulation, the 

 cleavage lines are interestingly shown through the transparent edge of 

 the blastoderm. From the radial arrangement of these furrows it can be 

 inferred that the embryo is travelling tail foremost over the animal pole 

 of the egg. And in a still later gastrula, Fig. I., it will be noted that a 

 number of large blastomeres are seen conspicuously through the con- 

 stricting blastopore. From the radiating lines which thus appear, we can 

 reasonably infer that the embryo has travelled still further backward. 



In order to give a more convincing idea of the appearance of 

 the above described cleavage lines, I have inserted, Figs. J-O, a few 

 photographs of the living egg. These show the lines clearly enough, 

 although, technically speaking, the pictures are faulty, for they were 



