480 MEMOIRS OF THE CARNEGIE MUSEUM 
that the nice restriction of certain periods in the seasonal history is primarily due to 
differences of temperature. It is only natural that an equalizing of the temperature 
must tend to efface the seasonal periods. 
4. Cambarus diogenes. 
According to my observations, which extend over the period from March 22 to 
November 17, this species also agrees in the main features of its seasonal develop- 
ment with C. obscwrus. 
I have the following records for females with eggs: April 6, 1905; April 19, 
1905; May 2, 1904; May 14, 1899, (collected by Atkinson, Graf, and Williamson) ; 
May 21, 1906; May 22, 1905; May 27, 1904. On May 21, 1906, and June 2, 1905, 
I found several females with newly hatched young under the abdomen. In no 
other part of the year has this been observed, and thus the spawning and hatching 
season is well fixed (April, May, and the beginning of June), and is found to be 
identical with that of C. obscwrus. 
The number of eggs is considerably less than in the case of C. obscwrus, and 
generally falls considerably short of one hundred. The spawning does not take 
place outside of the burrows, but inside of them, and this was most evident in a 
female collected on April 6, 1905, (Renfrew, Butler County), in which the eggs were 
quite fresh, with traces of the “apron” still visible. This female was dug out of its 
hole, as were all the rest with eggs or young ones. 
After hatching the young remain a short time under the abdomen of the mother. 
But soon they leave her, yet remain in the same hole. I have repeatedly found 
young specimens in the same hole with their mother, namely, on June 13, 1904; 
June 15, 1905; July 6, 1905; July 19, 1905. The smallest were about 10 mm. 
long. These young specimens generally occupy a separate part of the burrow, and 
are often found near to and inside of the mouth of a closed chimney. They remain 
in the hole until they attain a length of 20 mm., which happens toward the end of 
July. Then they leave the hole of the parent crawfish and begin to build their own 
little holes and chimneys. I observed this on July 26, 1904, at Derry, Westmore- 
land County, when I discovered a female 20.5 mm. long in a small hole of its own. 
At the same date I found a larger one, 30.5 mm. long, which may have belonged to 
the same generation. On August 4, 1904, at Francis Mine, near Burgettstown, 
Washington County, I found numerous young specimens between 20 and 29.5 mm. 
long, all in their own holes. On August 22, 1905, at Squaw Run, Allegheny County, 
I discovered two young specimens 22 and 28 mm. long. On August 26, 1905, at 
Baden, Beaver County, specimens 31.5 to 42 mm. long were found apparently under 
