90 DR. THOMAS ALCOCK ON THE 



time. The Plates accompanying this paper contain copies 

 of a selection of the drawings ; and the descriptions which 

 follow will serve to explain them. The numbers used, 

 agreeing with those on the Plates, are the number of days 

 since the ova were deposited, and give the age of each 

 specimen represented. 



Description of Plates. 



Plate I. 



3. I placed a single ovum in a watch-glass with water, 

 and examined it under the microscope with a one-inch 

 object-glass. The central part was uniformly opaque and 

 of a light brown colour by reflected light ; the surface 

 consisted of tubercles of unequal size, most of them rather 

 large ; they were slightly rounded, but flattened on the 

 top ; and their sides, where they were in contact, were 

 straight, forming angular figures, most frequently six-sided; 

 but in some cases they had three, four, or five sides ; and 

 they varied in size, a small one being here and there in- 

 terposed among larger ones. 



4. The surface of the ovum consisted of tubercles about 

 one sixth the size of those seen yesterday ; and their num- 

 ber was proportionately increased. They were remarkably 

 angular in shape. 



4 (2) . Six hours later they had become much smaller 

 and rounded. 



5. The surface was marked with an immense number of 

 very small tubercles; and a few slight irregular depres- 

 sions appeared here and there. 



On the 6th and 7th days there was no perceptible change. 

 The ovum continued perfectly opaque and of a light brown 

 colour ; and the surface was marked with minute rounded 

 tubercles of uniform size. 



