156 T. THOMSON FLYNN 



The pseudopodial processes characteristic of tlie plasmodium 

 of the previous stage are greatly in evidence in this stage also. 

 The residt is that spaces occur in the diploplasnia giving it a very 

 uneven appearance. The arrangement of these plasmodial 

 spaces suggests that new nuclei are formed in a somewhat 

 spasmodic manner in waves one after the other. 



One result of the advance of the plasmodium is the inclu- 

 sion of the maternal capillaries which pass up 

 between the remains of the syncytial lobules 

 and ramify 1j e 1 o w the layer of c y t o b 1 a s t . Each 

 capillary is contained in its delicate endothelial layer. Further 

 than this in the symplasmatic zone of the diploplasnia are to 

 be found remains of maternal nuclei, maternal blood corpuscles 

 and various granules. These are all obtained phagocytically. 

 An evidence of this action in the plasmodiblast is the strong 

 affinity which some of its nuclei have for pigment. In this 

 stage much of the pigment found in other cells of the previous 

 stage has disappeared. It is now almost entirely confined to 

 the cytoblast and plasmodiblast. Here it appears usually as 

 black granules deposited round the nucleus, but in other cases as 

 narrow irregular lines in the cytoplasm (figs. 25-27). A similar 

 pigment (related to haematoporphyrin ?) is found in Ungulates, 

 and is regarded by Jenkinson and Duval as being the remains 

 of ingested haematids whose iron has been passed on to the 

 embryo. The result is that the pigment remains in the tropho- 

 blast increasing in amount up to the time of parturition. 



Leucocytes. — These are extremely characteristic of the 

 uterine mucosa, particularly in the placental regions. They are 

 found in the connective tissue, from which they migrate through 

 the epithelium of the glands and mingle with their secretion. 

 They also pass into the diploplasnia, from which they reach the 

 extra-embryonal coelome. They can be seen abundantly 

 present in all sections of this region at this stage. In the 

 connective tissue they are small, taking the form of small 

 mononuclear leucocytes. In the diploplasnia, however, and 

 particularly when they reach the cytoblast, they have increased 

 greatly in size, forming large mononuclear leucocytes or macro- 



