COCOONS OF ALLOLOBOPHORA FtETIDA. 211 



were so little advanced in development that without a lens they 

 could not be detected until the slime-tube was removed from the 

 worm. Examination of the tube revealed an immature cocoon, 

 with a white semi-transparent covering, containing a much 

 smaller quantity of albumen than is found in mature cocoons, 

 but the eggs showed the stage of development found in a freshly 

 deposited cocoon, i. e., the first maturation spindle at the meta- 

 phase and in the center of the egg. Evidently the delicate cover- 

 ing of the cocoon is formed before the albumen is deposited, but 

 the substance that forms the chiton of the covering of the older 

 cocoons is not present, for we have preserved these immature 

 coverings in moist earth for twenty-four hours, and they failed 

 to become yellow and tough, like the covering of the mature 

 cocoon under these conditions ; they were white and soft at the 

 end of the experiment. 1 When the slime-tube is torn from these 

 immature cocoons, we find the covering of the cocoon consists of 

 two layers ; an outer, perfectly transparent layer, that can be 

 slipped off the inner covering, which is thinner, more resistant, 

 and semi-transparent. The former appears to be part of the 

 slime-tube substance that adheres to the cocoon, but in later 

 stages, when the cocoon is ready for deposition, this layer if pre- 

 served becomes yellow like the under layer, which indicates it 

 to be part of the covering of the mature cocoon. 



SPERMATHEC/E. 



In 10 per cent, of a large number of worms dissected, each with 

 a pronounced clitellum, all four spermathecae were found empty, 

 this proving that the appearance of the clitellum does not indicate 

 whether the spermathecae are full or empty, and also that cocoons 

 can be formed until the spermathecae are entirely empty. In a 

 few cases we found the spermathecae of copulating worms empty, 

 even when several spermatophores were present in the slime- 

 tube over the spermathecal segments, showing that, spermatozoa 

 are not received into the spermathecae during the early stages of 

 copulation. 



The condition of the individual spermathecae varies greatly. 

 Sometimes we found only one of the four entirely empty, and 



1 In only one case, an immature cocoon, with a trace of albumen and one egg, 

 showed this characteristic yellow tinge after three hours in water. 



