CONTRIBUTIONS TO THE ANATOMY OF THE HIRPDINEA. 433 



remain absolutely unstained by borax-carmine, while the con- 

 tents of the salivary glands take up a very deep staining. 



They do not exist in Piscicola, Pontobdella, Clepsine, 

 or Branchellion. 



I am unable to determine absolutely their function. Obser- 

 vations (Moquin-Tandon, Carena, &c.) show that the anterior 

 extremity is used in fastening the cocoon ; it seems possible 

 that the substance secreted by these glands may be used in 

 this operation. If this be the case, why are they not developed 

 in Pontobdella? Observations by M. Donadieu, which are 

 cited by Vaillant, show that the cocoon is seized by the 

 anterior sucker and pressed against some object, the animal 

 remaining in this position for some time. I do not consider 

 it at all likely that any secretion comes from the mouth, that, 

 to quote Vaillant " the pretended salivary glands " have any- 

 thing to do with this process, still less can any importance be 

 attached to the view of Ebrard that the nephridia (organes de 

 la mucosite) play any role in the matter. 



I think that so far as Pontobdella is concerned the entire 

 material for the cocoon must be secreted by the " clitellar " 

 glands, and that the anterior sucker can only function in its 

 moulding and attachment, the animal remaining in the position 

 described while the outer surface of the plastic substance 

 hardens. 



While working at the zoological station at Naples I kept 

 several living Pontobdella in a glass jar and five or six cocoons 

 were deposited,^ but I was unfortunately never able to observe 

 the process. 



We know little of the eggs of Branchellion or Piscicola, 

 and the eggs ofClepsine are not laid in a cocoon. 



If Pontobdella can form its elaborate cocoon without the 

 aid of these buccal glands, it seems unlikely that they can 

 exist in the Gnathobdellidae (which form simple cocoons) for 



' The cocoons never developed, and I have learnt from Professor Kleinen- 

 burg, of Messina, that he has obtained numerous cocoons laid in captivity 

 which have never develooed. 



