368 OLIGOCHAETA 



Considering the sum-total of these characters, I am quite inclined to agree with 

 MICHAELSEN, and to separate the species as a genus for which the name Pleionogaster 

 may be used. 



A form which doubtless merits generic separation is BOURNE'S P. stuarti. It seems to 

 come near to Megascolex fecundus in having two pairs of spermiducal glands, in common 

 with which the sperm-ducts open. Another peculiarity is the presence of modified 

 setae in the neighbourhood of the spermathecae. I have already proposed the generic 

 name of Hoplochaeta for this worm, but, pending further investigations by the discoverer 

 of the species, it had better perhaps be withdrawn. 



Five species, P. stelleri, P. everetti, P. papillata, P. saraivacensis, and P. Jcina- 

 baluensis, differ in the very remarkable character of possessing a large number of 

 spermathecae in each of the two segments where these structures occur. The 

 spermathecae are not, as for example in Microchaeta, of very small size. They are, 

 however, rather smaller than the paired spermathecae of Perichaetae of a similar 

 size. In addition to this point of difference, none of the species enumerated possess 

 intestinal caeca. They are all of considerable size, and are restricted to the islands of 

 the Indian archipelago, being especially characteristic of Borneo. It is possible that 

 they ought to be separated into a distinct genus, but I prefer to leave them in the 

 genus Perichaeta. 



Another doubtful form is my P. ceylonica. Its dubious position is largely owing 

 to the incomplete account which I was able to give of it. The arrangement of the 

 setae seems to indicate that the worm should be referred to the genus Perichaeta, 

 On the other hand, the absence of setae between the male pores, and the extension 

 of the clitellum on to the eighteenth segment, as well as the presence of penial 

 setae, are characters hitherto only met with in the genus Megascolex. Even dis- 

 counting the clitellum, which in one true Perichaeta is of equal extent, there is a 

 closer resemblance to Megascolex than to Perichaeta. The species is quite unique 

 among the Perichaetidae in possessing two pairs of glandular appendages to the 

 sperm-ducts, both situated in the same segment. Which of these is connected with 

 the sperm-ducts I am not able to say. For the present, pending further information 

 about the species, I refer it to the genus Megascolex. Another species, however, 

 ' Perichaeta ' fecunda of FLETCHER, has two pairs of spermiducal glands ; these do not, 

 however, as in M. ceylonicus, open on to the same segment, but on to the consecutive 

 segments xviii and xix. A bilobed spermiducal gland, which is the earliest or latest 

 stage in the same series, occurs in Megascolex. 



The distinctness of this genus is somewhat marred by SPENCER'S P. dendyi ; there 

 are several ' Perichaetes,' which agree with the New Zealand form in having tubular 



