PATHOLOGIC OVA, ALBINO RAT 117 



It is my primary purpose to make r< cords of the abnormal ova 

 observed in the material at hand; and to follow these records with 

 a brief consideration of the observations made. There is no 

 literature dealing with the problem immediately at hand abnor- 

 mal rat ova. It is not my purpose at this time to enter into the 

 extensive literature of comparative experimental teratology. 

 This has been critically summarized relatively recently by 0. 

 and R. Hertwig, and by Mall, in his several contributions deal- 

 ing with human pathologic ova. 



HALF EMBRYOS IX MAMMALIA 



The first preparation to which attention is called is one taken 

 from the oviduct of rat No. 60, 1 day, 18 hours, after insemina- 

 tion. The two oviducts of this rat contained seven ova in the 2- 

 cell stage, to one of which especial attention was drawn in Part I 

 (page 271). As there recorded, in one of the 2-cell stages, the 

 first two blastomeres were separated by an appreciable distance. 

 There is loss of oolemma. The possibility of half embryos in 

 Mammalia was suggested. The preparation under consideration 

 is figured in figure 1, A and B. In A of this figure there is pre- 

 sented a portion of the wall of the oviduct, its epithelial lining 

 and the immediately adjacent mucosa, including the fourth of a 

 series of six sections (10 n) passing through the two blastomeres. 

 In this region, the cilia of the epithelium are clearly observable, 

 as may be seen from the figure. In B of this figure there are 

 sketched in approximately relative position the several sections 

 of the series passing through the two blastomeres, the relative 

 position of which, with reference to the walls of the tube, is shown 

 in A of the figure. The six drawings were made from a well 

 ribboned series; the slide was moved from section to section by 

 means of a mechanical stage, and the perpendicular indicated on 

 each drawing as made. The relative position of the several 

 drawings, therefore, is quite correct. It may be observed that 

 throughout the series the two blastomeres are separated by an 

 appreciable space, and that one of the cells has rotated slightly 

 on its axis. If these two blastomeres had remained in close appo- 

 sition, they would present the appearance of a normal 2-cell stage 



