14. The Paraphysis in the Common Fowl 
First. The epiphysis. Srconp. The supra-commissure. 
Tuirp. The post velar arch. This extends from the supra-commis- 
sure to the velum. 
FourtH. The velum transversum. Firra. The paraphysal arch. 
This extends from the lamina terminalis in front, to the velum trans- 
versum behind. It is in this subdivision, close to the velum, that the 
paraphysis is found. 
The history of the paraphysis in the lower vertebrates has been re- 
peatedly studied and described. It is curious that so little attention 
has been paid to it in birds, especially since its presence has even been 
demonstrated in certain mammalan embryos. Selenka (12) was the 
first to identify the paraphysis in chicks. Burckhardt (1) mentions it 
in a 2.5 mm. embryo crow, and states (2), “In birds the paraphysis 
remains rudimentary and later cannot be identified.” Minot (9) also 
refers to it in an embryo chick of about seven days. D’Erchia (5) 
identified the paraphysis in fish, and in mammalian embryos, and be- 
hieves it to be a constant structure in all vertebrates, but reports no 
observations on birds. Francotte (7) identified it in a human embryo 
of twelve weeks, and believes it to exist in all vertebrate embryos. This 
is all the literature I have been fortunate enough to find relating to 
the paraphysis of birds. 
Many of the preparations employed in this piece of research work 
belong to the Harvard Embryological Collection. Besides the sections 
here represented, intermediate stages of embryos were studied, as well 
as chickens varying from a few days to full-grown hens. The sections 
were invariably serial, and double stained with cochineal and orange G. 
Many specimens were hardened in Tellyesnicky’s fluid, which gave on 
the whole better results than Zenker’s, and of course has the great 
advantage of being without corrosive sublimate. Thirty-six hours was 
perhaps the usual time the adult brains were allowed to remain in this 
fluid, and an equal amount of time in running water, and then they 
were treated by the progressive alcohol method. Great difficulty was 
experienced in making true longitudinal median sections of the adult 
brains. This was largely due to the depth of the longitudinal fissure 
and to the very thin inner wall of the lateral ventricle, which often in 
the process of hardening becomes more or less twisted. Much less 
difficulty was usually encountered in the earlier stages where the entire 
head was cut without removal of the brain. Nos. 1, 2, 3, 4, 5 and 7 of 
the following figures were drawn on the same scale, and all of the sec- 
tions in this paper were drawn with the aid of a camera lucida. 
Figure 1 is a sagittal section of the forebrain of a 6.7 mm. embryo. 
