178 BRACE. [Vol. XVII. 



tutto la linea mediana ventrale dell' animale mandando laterala- 

 mente degli esili fili nervosi, ed un ganglio cefalico consti- 

 tuiscono per quel che potei scogere, il sistema nervoso degli 

 Aeolosoma." This description has not generally been credited. 

 He gives no illustrations of the nervous system, and his drawing 

 showing the mouth at the end of the prostomium, with the space 

 inside the prostomium designated as the buccal cavity, leaves 

 no place for a brain and is incorrect, as well as the statement 

 that the nerve cord extends along the median ventral line. 



Beddard ^ says of A. tenebrariivi : " This species alone shows 

 any traces of a ventral cord, which is very short and is not 

 connected with the brain." 



A further study of the subject was undertaken in the Zoo- 

 logical Laboratory of the University of Chicago, at the sug- 

 gestion of Professor C. O. Whitman, to whom I am indebted 

 for the supervision of my work. 



Material for study was found among the water plants in the 

 park ponds of Chicago, where it was especially abundant around 

 the water hyacinth and Victoria regia. 



The worm is not an active swimmer, but prefers to lie among 

 the algae or to crawl between the meshes of a decaying leaf. 

 It is white and semi-transparent, and the integument is studded 

 with innumerable green oil drops contained in gland cells 

 which have their large nuclei flattened against the cell wall, 

 similar to the gland cells of the Turbellaria. A delicate chiti- 

 nous covering may be seen after treatment with reagents. The 

 worms feed upon algae or bits of decayed leaves and have a 

 tendency to collect on the sunny side of the aquarium. They 

 vary in length from 3 to 10 mm. 



A number of worms will frequently get together, twist them- 

 selves into a ball, and remain so for a long time. It has been 

 suggested that this was connected with conjugation, but that 

 is improbable ; they are presumably feeding upon each other, 

 as one worm is usually found partly eaten, if the ball is pulled 

 apart. They have great powers of regeneration ; in one case, 

 where the head had been eaten away to the first pair of setae, 

 a new head was regenerated in about three days. 



^ Beddard, F. E. A Monograph of the Order Oligochaeta. 1895. 



