No. 5-] STRUCTURE IN AN ABNORMAL PIGEON. 215 



the group, b, bi, c, ci, really formed a cluster of four. The next 

 group, d, d\, dz, formed a set of three, and the last egg, e, was 

 double. 



Almost all gradations of union between the two related 

 egfsfs could be seen. In some cases there seemed to be but one 

 mass of cytoplasm containing two nuclei (Fig. 9) ; in others a 

 dividing membrane was present, but was incomplete. In still 

 other examples there was a distinct membrane between the 

 eggs, together with a few strands of connective tissue, with the 

 follicle cells at the edges apparently creeping gradually in along 

 the line of demarcation. Occasionally scattering follicle cells 

 were found between the two eggs. 



Most of the double forms were of small diameters. When 

 large eggs were doubled they seemed to be in a state of degen- 

 eration. They contained large vacuoles, and, perhaps, in addi- 

 tion the cytoplasm was being consumed by phagocytic action. 

 Fig. 4 represents four sections taken in order at varied places 

 from one of the larger double eggs. At A (Fig. 4), in one of 

 the eggs, the nucleus is shown. It is considerably shrunken. 

 A faintly marked cell wall separating the two eggs is visible, 

 and lining it on either side is the material of the so-called 

 attraction sphere or yolk nucleus (s). The follicle cells at one 

 edge (/) have lost their walls and form a sort of syncytial mass. 

 At B (Fig. 4) the section shows the membrane which separates 

 the two eggs as still visible. The nucleus of the other egg has 

 come into view and is also much shrunken. At this point the 

 sphere substance is seen to project out more toward the center 

 of the upper egg, and in the center of this mass a clear space 

 or vacuole {i>) is visible. As the sections are passed over, this 

 vacuole rapidly becomes larger and appears as at C and D 

 respectively. In C there is no trace of a dividing cell wall, and 

 the cytoplasm of the two cells mingles. In the sphere sub- 

 stance of the lower cell a second vacuole has made its appear- 

 ance, and it gradually merges into the first, as seen in D. 



The formation of vacuoles is very common, especially in the 

 larger eggs, both single and double. In some of the eggs, 

 indeed, most of the cytoplasm has disappeared, and only a large 

 vacuole remains. Vacuolation begins invariably in the sphere 



