438 On the Nature and Origin of the [May, 
Mr. A. S. Kent, of San Rafael, California, who for many years, 
on account of his health, spent several months each year in 
camp life in the mountains, principally hunting the deer, informed 
me that he once purchased a couple of cubs of the grizzly bear, 
which he took into camp with him. One of these proved very 
docile and tractable, and seemed fond of his attention and society, 
and usually slept contentedly at his feet. The other seemed pos- 
sessed of a much more vicious disposition, and he was obliged 
to kill it. Possibly this might have been overcome by patient 
care and judicious training. 
There is no doubt that different dispositions among these ani- 
mals as among most other, may be met with. 
Mr. Kent’s observations tend, in some degree at least, to con- 
firm those of Mr. Adams. 
May we not hope that some one with the necessary taste and 
proper facilities will try experiments and give us the benefit of 
their observations ? 
A complete monograph of any one of our species of bears 
_ under all conditions would be a valuable addition to our zoologi- 
cal literature. 
—.0: 
ON THE NATURE AND ORIGIN OF THE SO-CALLED 
“SPIRAL THREAD” OF TRACHE#:. 
BY A, S. PACKARD. 
HILE we owe to Professor O. Biitschli the discovery of the 
mode of origin and morphology of the trachee, which as 
he has shewn? arise by invaginations of the ectoblast ; there being 
originally a single layer of epiblastic cells concerned in the forme 
tion of the trachee; we are indebted to Professor A. Weismann 
ae _ for the discovery of the mode of origin of the “intima,” from the 
. epiblastic layer of cells forming the primitive foundation of the 
=` tracheal structure. We are also indebted to Weismann for the 
discovery of the mode of origin of the terminal tracheal cells. 
Weismann did not observe the earliest steps in the process 
of formation of the stigma and main trunk of the trachee, which 
Biitschli afterwards clearly described and figured. 
Weismann, however, thus describes the mode of development 
1870. 
1 Zur Entwicklungsgeschichte der Biene, Zeit. wissen. Zoologie, XX, 51% 
= *Die Entwicklung der Dipteren im Ei. Zeit, wissen, Zoologie, X111, 1863- 
