NOTES ON THE NAIDIFOEM OLIGOCH^TA. 347 



new region elongates, and presents a solid appearance. The 

 alimentary canal grows in this region, but the newly formed 

 portion is at first unpigmented, and may still be detected at a 

 much later period by its lighter colour. Its lumen remains, 

 however, all the time, and a continuous line of faecal matter 

 may be observed (PL XXVII, fig. 9,/«c.). This budding region 

 divides into two portions. The anterior portion develops 

 numerous setae, and gives rise to an indefinite number of 

 segments which form the tail of the old worm. The posterior 

 portion develops four pairs of ventral setse, this development 

 taking place from before backwards ; and subsequently at its 

 anterior region the peristomial segment and the characteristic 

 proboscis are developed, and the two individuals separate. The 

 budding region usually forms between segments xxvii and 

 XXVIII, so that segment xxviii becomes segment vi of the 

 posterior daughter worm : the five anterior segments of this 

 worm never present dorsal setae." 



What is described above as taking place is clearly shown in 

 PI. XXVII, figs. 7 — 9, which represent various stages of the 

 process. 



The division of the budding zone into a new tail on the one 

 hand and a new head on the other was clearly stated by 

 Semper,^ whose paper on the subject I had not seen when 

 writing the above. 



It will be seen that, according to the nomenclature I have 

 adopted, n = 26, and z' consists of five segments in this 

 species. 



Pterostylarides, Czerniavsky (see woodcut). 



Four cephalized segments in addition to the peristomial 

 segment are indicated in the fully grown worm. The two 

 hinder of these are devoid of ventral as well as of dorsal setae. 



The prostomial tentacle is of medium length. 



The dorsal setae are capillary. 



There are no branchial processes. 



Eyes are present. 



Vejdovsky associates this genus with Stylaria, but I think 



' * Arb. zool. zoot. Instit. Wurzburg,' Bd. iv, 1877. 



