484 FOOT. [Vou. XIV. 
represented in Fig. 3 by the thread-like extension. Owing to 
the rapidity with which the worms separate, I have not been 
able to satisfy myself definitely on several points relating to 
the formation and deposition of the cocoons. 
In Fig. 1 are seen four denser, cord-like portions of the 
slime-tube, circling the anterior and posterior edges of the 
clitellum of each worm, and binding closely against it three 
(9-11) of the anterior segments of the other worm. These 
cord-like portions seem to have contracted until they press 
into the bodies of the worms like a thread tightly wound around 
them, and they are so tough that by slipping a needle under 
any one of them, both worms can be lifted from the table in 
spite of their efforts to separate and escape. Possibly they are 
differentiations of the slime-tube; possibly they are of the 
same secretion that forms the cocoon, though they are present 
before the slzghtest indication of a cocoon can be detected. 
They narrow the lumen of the slime-tube (Fig. 2) in planes 
finally occupied by the ends of the cocoons, suggesting that 
they may later aid in closing the cocoons. 
When the cocoon is first deposited, its case is perfectly white, 
less opaque than the albumen within it, and nearly as soft as 
the slime-tube. It does not acquire the slightest tinge of yellow 
until some minutes after deposition. Exposed to the air, it 
very rapidly changes color, becoming first a delicate pinkish 
straw-color and assuming later the more distinctly yellow tone. 
As it acquires this yellow tinge, it becomes more resistant, and 
finally attains its hard chitinous character. An immature 
cocoon changes color much less rapidly. After opening such 
a one and preserving the eggs, the case of the cocoon remained 
white for more than an hour, and after five hours had acquired 
only a delicate yellow tinge. This appears to indicate that the 
secretion which forms finally the chitinous constituent of the 
case is not formed at the earlier stages of the construction of 
the cocoon. 
The slime-tube of the freshly deposited cocoon is transparent, 
adhesive, and elastic, adhering so closely to the soft white 
cocoon that it seems part of it and it is difficult to separate the 
two. As the cocoon becomes yellow and attains its hard 
