SECT, ix EXCRETORY AND OTHER GLANDS 129 



A long chitin-lined duct opens into a similarly lined 

 vesicle. 



(3) In the "salivary" gland the chitinous sac ends 

 blindly, the end being fastened by muscle bands to 

 the body wall, exactly as is a setiparous gland of the 

 Annulata. In the shell gland, however, the sac or 

 bladder is continued into a long coiled urinary canal. 1 

 The position of this urinary canal in the dorsal fold, 

 and the finer structure of its walls, seem to indicate 

 that at least this part of the gland is a new formation. 

 It in no sense reminds one of an Annelidan nephri- 

 dium. 



(4) These arguments are especially strong if the 

 rest of our argument holds good, viz., that Apus is 

 but a slightly transformed Annelid, or, indeed, if 

 we only claim what is often admitted, that the 

 Phyllopods stand nearest the racial form of the Crus- 

 taceans. If even this latter alone is the case, the 

 shell gland of Apus, if a true nephridium, should 

 show more likeness to a nephridium than do the 

 shell glands of the higher Crustacea, which have 

 departed further from the Annelidan type. \Ye 

 should expect the shell gland in Apus to be a 

 transition form between the Annelidan nephridium 

 and the Crustacean shell gland, just as we found the 

 " liver " of Apus to be a true transition form between 

 an ordinary digesting diverticulum such as is common 

 among the Annelida, and the purely glandular hepato- 



1 Grobben says that the whole canal in the antennal gland of Mysis is 

 lined with a chitinous cuticle. In Apus, however, the intima ceases 

 with the bladder. 



K 



