26 ALICE M. BORING AND RAYMOND PEARL 
activity of the ovary. No. 1429, Atwood’s bird, and the Michi- 
gan bird have many oocytes of varying sizes on the periphery. 
No. 1349 and 1426 have some cystic oocytes, while there are 
corpora lutea representing discharged or atretic follic'es on 
four birds, 1426, Atwood’s bird, 1349, and the Michigan bird. 
No. 1429 has no discharged follicles, nor any very small oocytes. 
No signs of ovarian activity, either past or present could be 
discovered in the other three birds, 1428, 1427, 1425. 
The only birds with active testis in which sperm were 
observed are Bond’s pheasant, 1426, 1349, and 1616 described 
in this paper, possibly also the three birds of Hammond Smith, 
although we do not know how carefully the histology of these 
was studied. It should be noted that all eight birds described 
by the present authors may be interpreted as fundamentally 
females, some of them checked in the embryonic condition of 
the gonads, and some of them changing over to a male condition. 
Next in the series of abnormal birds we have placed the 
guinea chicken hybrids. The anatomy of these is apparently 
that of perfectly normal males with two testes and two vasa 
deferentia. These were of normal size in one, and much en- 
larged in the other. That these testes, however, are not normal, 
is clearly shown in microscopic sections (fig. 31). There is no 
sign of tubules or any cells distinguishable as germ cells. The 
structure looks more like ovarian stroma than part of a testis, 
that is absolutely indifferent, whether ovarian or testicular in 
nature. In fact, it is probably neither, but simply an undif- 
ferentiated gonad, as in the early embryo. Neither are there 
any cells with the distinguishing marks of interstitial cells or 
lutear cells. This is, of course, an. entirely different condition 
from that found in Guyer’s guinea chicken hybrids, where there 
were many tubules and an abnormal synapsis either stopped 
the process of sperm formation or else resulted in abnormal 
spermatozoa. Poll has worked out the theory from his hybrid 
birds that the more closely related two crossed birds are, the 
more normal will be the spermatogenesis. This, however, does 
not explain how some male guinea chickens can have abnormal 
