144 OLIGOCHAETA 



Perichaeta ■pokthuvia there are only two pairs, one on the segment in front of, and 

 one on the segment behind, that which bears the male-pores. In Perichaeta indica 

 there are no papillae near to the male-pores, but three pairs on the segments which 

 bear the spermathecal orifices. Now in all these cases the papillae are little more 

 than the external pores of glands, to which I have given (78) the name of 

 ' eapsulogenous glands ; ' it sometimes happens that a large number of these glands 

 are associated together ; in that case there are a group of papillae ; the species 

 Perichaeta aspergillum and Perichaeta bermudensis are partly characterized by the 

 fact that in the neighbourhood of the male-pores, or near to these and to the 

 spermathecal pores, are a group of orifices which belong to a mass of such glands. 

 In Perichaeta, hilgendorfi, Beddabd (30), there is a median unpaired group of such 

 orifices upon the eighth segment. 



The glands which are associated with these papillae are solid masses of pear-shaped 

 cells, which are no doubt of epidermic origin ; they have long stalks, which penetrate 

 the epidermis and reach the exterior; the stalks have a fibrous aspect, for they are 

 simply the prolongations of the cells ; the glands in fact, in spite of their compound 

 appeai'ance, are merely groups of unicellular glands ; very commonly the mass of 

 gland-cells are bound together in a common sheath ; this is, for instance, the case 

 with the species Perichaeta hilgendorfi just referred to ; I have figured in this 

 species a mass of these glands which are enclosed in such a sheath ; it sometimes 

 happens that these glands do not open directly on to the exterior ; the two species 

 Perichaeta houlleti and P. d'udekenii (if they be really distinct) are each provided 

 with one or two pear-shaped glands, attached to the stalk of the spermathecae, 

 which have been termed diverticula of tlie spermathecae, but which, as I showed, 

 are merely glands of a kind perfectly similar to the 'eapsulogenous glands' — 

 different only in the fact that they do not open on to the exterior direct, but 

 through the spermathecal duct ; so that when these species are described as having 

 no papillae, it must be remembered that they have the glands which in other 

 forms are associated with papillae. The function of these papillae is a matter of 

 doubt ; more generally they have been held to be organs which allowed the worms 

 to maintain a fii-m hold upon each other during coitus ; I have suggested that their 

 function may be that of producing albumen for filling the cocoon ; and have in 

 consequence compared them to the so-called eapsulogenous glands of the Lumbricidae — 

 glands which occur in the neighbourhood of the spermathecae, but whose structure 

 is at present not known. No direct observations are on record which would enable 

 this question to be decided. 



Among the Lumbricidae the papillae are represented by the structures first called 



