Ban 
chens”, Archiv für Anat. und Entw., 1887, suggests the rather novel 
idea that the common carotid may be due to an extreme lengthening 
of the dorsal connections between the third and fourth arches — the 
basal portion of the third arch having atrophied. 
HocnstTerTer’s!) account of the probable development of the 
arteries in birds, in the light of observations on reptiles (crocodilia), 
is the best so far given. He suggests that there is an anastomosis 
between the ventral and dorsal vessels which afterwards breaks down 
accompanied by a great shortening of the remains of the ventral vessel. 
This proves to be the case, but, the steps in the formation of this 
anastomosis, and the retrogression of the ventral vessel have never, | 
so far as I am aware, been figured nor described. 
TANDLER?) in a recent paper (1902) has given a very complete 
account of the formation of the carotid in the human embryo and 
the rat, and, since the process of formation is different in birds, it is 
now all the more desirable that we should have the question of their 
development worked out in that group of animals. 
Personal Observations. 
The following paper prepared under the direction of Professor 
Wm. A. Locy aims to give an objective account of what actually takes 
place in chick embryos in the formation of the carotid artery. The 
difficulties of following the history of these blood vessels in the embryo 
are considerable because the changes are extensive and come about 
so insiduously that they are not easy to follow nor to understand. 
The observations extended over a period of two years (1904-05 
and 1905-06). It is a pleasure to acknowledge my obligation to 
Professor Locy both for suggesting the problem and for his assistance 
in all stages of the work. 
Chick embryos were studied. A carefully graded series was in- 
cubated and the age of development compared with Duvar’s Atlas 
d’embryologie. Observations were begun on living embryo but the 
carotid arteries lie so deep in the tissue that no trustworthy results 
were obtained. Therefore, in the end, injection and dissection were 
used and the results obtained were verified by the study of sections. 
In critical stages a large number of preparations both of injected and 
1) Ferpinann HocHSTETTER, Die Entwickelung des Blutgefäßsystems. 
Handbuch der vergleich. u. experiment. Entwickelungslehre der Wirbel- 
tiere, herausgeg. von Oscar Hertwie, 1904. 
2) JuLıus Tanpuier, Zur Entwickelungsgeschichte der Kopfarterien 
bei den Mammalia. Morph. Jahrb., 1902. 
