BY WILLIAM A. HASWELL, M.A., D.SC. 579 



The various parts of the egg have precisely the same relations as 

 in the fowl ; the white is rather less in proportion to the yolk ; but 

 there is no other dift'erence of importance. The yolk is about seven 

 and a-half centimetres in its long, and seven in its short diameter; 

 the long axis coincides with that of the egg ; and usually there are 

 discernible a broad end and a narrow end corresponding with the 

 broad and narrow ends of the egg itself. 



The embryo was usually found to lie with its long axis at 

 right angles with the long axis of the yolk and of the egg ; 

 but not unfrequently the position was oblique, though never 

 longitudinal. 



The unincubated blastoderm was of nearly the same size and 

 appearance as in the fowl, and was not made the subject of special 

 examination. In eggs incubated for from about forty-seven to fifty 

 hours the entire blastoderm was about a centimetre in diameter ; 

 the area pellucida was two millimetres in diameter, and with a 

 dark patch, the 'embryonic shield,' in the middle. 



A blastoderm of fifty-one hours was the eai'liest of which a 

 thorough study was made. The entire blastoderm was a centi- 

 metre in breadth and the area pellucida three millimetres in its 

 greatest diameter. The area pellucida presented two regions — an 

 anterior which was rounded and rather broader than long, and a 

 posterior, which had the appearance of a very short and narrow 

 bay of the anterior part. This postei'ior bay (the ' Zuwachsstiick' 

 of His) is the commencement of the primitive-streak region, and 

 presents an indistinct dark axial band which is tlie commencement 

 of the primitive streak. In no part was there a trace of a primitive 

 groove. When examined in sections this blastoderm was found to 

 consist throughout of only two completed layers — an upper and 

 a lower. In the anterior larger part of the area pellucida these are 

 separated throughout by a well-marked interval. In the posterior 

 bay they are confluent along the middle line — forming the 

 primitive streak. A little distance in front of the anterior end of 

 the primitive streak the lower layer presents in the middle a slight 

 thickening of no great extent. This is the earliest rudiment of 



