DEVELOPMENT OF SPELERPES BILINEATUS 



221 



Series B. Eggs in early cleavage stages, marked May 16, 

 6:30 P.M. and immediately drawn. No. 4, fig. 45. Four small 

 spots were made upon the upper surface of the egg around the 

 upper pole which is indicated by the cross. It lies a little eccen- 

 tric. May 18, 12 m. (fig. 46). The stain has spread and now 

 forms a small patch in the region occupied by the original spots. 

 Records made at intervals show no further changes in the stained 

 areas. May 23, 11 a.m., the sketch shown in fig. 47 was made. 

 The stain lies well within the neural folds on the left side. One 

 end crosses the anterior end of the neural groove. The egg has 

 rotated somewhat (see page 191). I conclude that the anterior 

 connective must have been formed some distance beyond the 

 upper pole. 



The results obtained from the other eggs while similar, show 

 that as stated above, some variation exists in the location of the 



45 



46 



47 



Figs. 45-47 



anterior connective. Provisionally we may say that the anterior 

 connective develops 25°, on the average, anterior to the upper 

 pole. The advance of the dorsal lip is also variable. Still, I 

 think we shall not be far wrong in assigning, provisionally, a 

 value of 35° to its advance. If, now, it appears 35° below the 

 equator, we find that its median part finally lies 70° below the 

 equator. (The free ends of the blastopore may reach further.) 

 This would give the embryo an extreme length of 185° when it 

 first appears. This figure is not far from correct. I have not 

 measured the embryo, but in preserved material, the anterior 

 connective at its first appearance lies about opposite the blasto- 

 pore. In a few eggs studied in sections, the embryo appears to 

 be only 160° long, while I have a camera drawing of another, in 

 which the anterior connective at the stage shown in plate 1, fig. 9 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 12, NO. 2 



