Vol. 6, 1920 
ZOOLOGY: G. A. BAITSELL 
77 
Has the model figured in this paper any value either to confirm or to 
disprove the linear hypothesis? It does not, like the models of chromo- 
somes 1 and 3, show the genes in a curved band lying in one plane. But it 
does show them lying roughly in a linear chain winding cork-screw fashion 
through the model. If all wires over 40 inches long were cut, the system 
would straighten out so as to approach a linear arrangement. I conclude 
that the model supports the linear hypothesis, if it be supposed that the 
longer distances have been shortened by double crossing-over, and that 
map distances in such cases should exceed observed cross-over percentages. 
1 These Proceedings, 5, 25, 32, and 500. 
2 Carnegie Inst. Washington, Puhl. 237, 1916. 
3 Genetics, 3, 1918 (107-134). 
4 Bridges, C. B., and Morgan, T. H., "The Second Chromosome Group of Mutant 
Characters," Carnegie Inst. Washington, Puhl. 278, 1919 (123-304). 
5 Gowen, J. W., "A Biometrical Study of crossing Over." Genetics, 4, May, 1919 
(205-250). 
6 These Proceedings, 5, May, 1919. 
7 Haldane, J. B. S., Genetics, 8, Sept., 1919 (306). 
THE DEVELOPMENT OF CONNECTIVE TISSUE IN THE 
AMPHIBIAN EMBRYO 
By George A. Baitsell 
OsBORN Z001.OGICA1. Laboratory, Yale University 
Communicated by R. G. Harrison. Read before the Academy, November 10, 1919 
The researches^ in which the author has been engaged for several years 
have shown, in brief, that the structure of the plasma clot of frog's blood 
is of such a nature that when influenced by the proper mechanical factors, 
e.g., tension or pressure, its structure will be radically changed. In cases 
of this kind a fusion and consolidation of the minute elements of the 
clot will take place and, as a result, long fibers will be formed which unite 
in wavy bundles, anastomose with other bundles and ramify in various 
directions throughout the clot, thus resulting in the formation of a material 
which, at least in its morphology, is like certain types of connective tissue. 
In wounds in frog's skin, the experiments showed that a fibrous tissue 
formed from a plasma clot functioned, at least temporarily, as a normal 
connective tissue and there was no evidence to show that it would ever 
be replaced. 
The above results led naturally to the question as to whether a similar 
process normally takes place in the histogenesis of connective tissue in 
amphibian embryos. The results obtained from these investigations are 
as follows : 
1. The primitive forerunner of connective tissue in frog embryos is a^ 
amorphous, gelatinous material which, because of the fact that it stains 
