280 OLIGOCHAETA 



A worm divides at a given spot (probably characteristic for the species) i; at this 

 point growth takes place and a number of new segments are formed which are in 

 two series, one on either side of the line of division already referred to. The anterior 

 set consists of an indefinite number of segments and form the tail of the anterior of 

 the two worms (produced by division of the original worm). The posterior set consists 

 of a definite (and characteristic) number of segments which will form the head of the 

 second worm. 



Kallstenius has described the same process in Amphichaeta. The worm which 

 is not budding consists of seven segments. The first step towards asexual multipli- 

 cation is the production of an eighth segment which comes to be separated from the 

 seventh segment by a budding zone. This eighth segment becomes the fourth of 

 the daughter bud, the three anterior being formed from the budding zone and those 

 behind from the original segment— the eighth of the parent. The two individuals 

 then come apart, leaving a budding zone and an' eighth segment upon the parent, 

 which gives rise to further division. 



The process may be graphically represented thus : — 



In considering the genus Aeolosoma I have pointed out the characters of certain 

 species which form a transition to the Naidomorpha. Voeltzkow has observed in 

 Madagascar a form like N. lacustris, which has in the integument numerous colourless 

 oil-drops ; these are said to present almost the appearance of a black pigmentation. 

 Chaetogaster, too, is said to have colourless oil-drops in the integument, and both these 

 forms so far approach Aeolosoma, particularly A. niveum. 



There is one genus of wliicli I do not give a deliberate description with synonyms, &c., as its 

 systematic position cannot at present be fixed with certainty. 



The position of Vetrovermis hyalinus is uncertain. It is described by Imhop as occurring in 

 several lakes in Switzerland. The body is not ciliated, and there are only one pair of setae 

 bundles in each segment. 'The setae are thin, quite straight up to either extremity, where they 

 are easily bent from side to side ; at the free extremity they are bifid.' There is a swelling at the 

 end of the first third of the seta. It multiplies by division, and sexual organs were not met with. 



' Not so, according to Benham (9), at least not for A', barhata and JV. lacusiris. 



