42 
SPERMATOGENESIS OE NORMAL 
decay. Fig. 45 represents a common example where the 
nuclear contents have a watery and disintegrated appearance and 
the sphere substance is marked by the presence of a large 
vacuole in its center. Fig. 46 represents another common type 
in which one or more vacuoles appear in the nucleus. In Fig. 
47 the spermatocyte has evidently prepared for division, as 
evidenced by the eight chromosomes, but for some reason was 
unable to proceed. The chromosomes have remained intact 
but have scattered throughout the cell. 
Fig. 48 represents a type of very frequent occurrence. A 
number of cells have run together to form a giant cell in the 
center of which is an enormous vacuole. This last type is one 
very similar in appearance to the giant cells found in many 
pathological tissues. Fig. 50 shows a degenerating cell in 
which there are four groups of chromosomes. Each group is 
made up of four chromosomes. This curious arrangement is 
due probably to the fact that a cell like Fig. 29 has divided, but 
has ceased its activity immediately after division before the 
new nuclei had time to develop. 
THE INDIVIDUAL HISTORIES OF THE STERILE FORMS. 
Before leaving the subject of the abnormalities in the hybrid 
forms, it seems desirable to run over briefly the individual cases 
that have been studied. The most important facts only arc 
touched upon. The birds are described in no particular order. 
I. Age, 14 months. Parentage: male, tumbler; female, 
brown ring dove. The testes were large and from an external 
point of view fully developed. The ducts and genital papillae 
were normal. Degenerative processes were going on in many 
of the tubules but not so extensively as to prevent the forma¬ 
tion of innumerable spermatozoa of the curious beaded type 
represented in Fig. 40. Giant cells (Fig. 48) were numerous 
as were also many vacuolated spermatocytes of the type rep¬ 
resented in Figs. 45 and 46. Multipolar spindles and asymmet¬ 
rical distribution of chromatin were very frequent in division. 
II. Age, 18 months. Parentage: Male, black tumbler; 
female, brown ring dove. Much the same condition prevailed 
as in Hybrid I. Not so many spermatozoa were formed and 
