378 C. O. WUITMAN. 



according to Dursy and Balfour, the commencement of the 

 notochord. 



The primitive groove does not end at the hindmost point of 

 the area pelkicida, but curves to the right near where it leaves 

 the shield, and passes on through the area opaca, ter- 

 minating IN THE MARGINAL NOTCH. The primitive streak 

 cannot be followed beyond the inner edge of the area opaca. 

 Not the slightest trace of a falciform expansion^ of its posterior 

 end could be detected. No head-fold has yet appeared to mark 

 the limit of the prolongation of the primitive streak. 



The only exceptional feature of this blastoderm is the con- 

 tinuation of the primitive groove to the marginal notch j and I 

 believe this is the first time that such a feature has been re- 

 corded. Balfour, His, Rauber, and others have expressly 

 stated that they have never been able to trace this groove to 

 the margin of the blastoderm. Rauber, His, Balfour, and 

 Pander have observed cases in which a marginal notch was 

 present, but not a single instance where the groove extended 

 to the notch. Although this is probably the first time that 

 such a peculiarity has been described, I cannot say that it is 

 the first time it has been observed. Indeed, I happen to know 

 that one other similar case was found only a few days before I 

 obtained the one here described. It was my friend, Dr. A. 

 Bohm, the present assistant of Professor KupfFer, who found 

 the first case. What use he has made of his preparation 1 

 cannot say, but I am quite certain that he has never published 

 any account of it. I have long deferred the publication of this 

 paper in the expectation that Dr. Bohm would make known 

 his discovery, and in the hope of obtaining another specimen 

 myself for sections. As neither of these events have been ful- 

 filled, I have decided to describe the blastoderm in my pos- 

 session. 



As to the fact that the primitive groove extends to tlu' 



notch, there is no room for a shadow of doubt. That arm of 



the groove which passes through the area opaca could be seen 



with the naked eye even before the blastoderm was cut from 



I See Kupffor, 27, 28, 29, 30. 



