STRUCTURE OF TWO NEW GENERA OF EARTHWORMS. 263 



But in Heliodrilus there are some diflPerences of detail. 

 The expanded portion of the vas deferens^ which lies in front 

 of septa 10, 11, and 11, 12, is proportionately much larger, 

 while the narrow neck by which it is connected with its funnel 

 is much longer than in Hyperiodrilus. 



Furthermore, the expanded portion lies in the ccelomic space 

 which contains the testis, or rather it is closely invested by a 

 narrow space (figs, 11, 16, and 18, coelom), which is perfectly 

 continuous with that enclosing the testis. Sections show that 

 there is no real demarcation between these spaces, which form 

 on each side a pair of sacs — one larger enclosing the vas 

 deferens, and one smaller containing the testis. It should be 

 mentioned that the vas deferens itself on the posterior side of 

 each of the septa lies quite freely in the coelom. 



The dilated region of the vas deferens is quite similar in 

 structure to the rest of the tube ; it is lined by a layer of 

 low columnar ciliated cells, and is invested by a sheath con- 

 taining a few muscular fibres. The interior, as in Eudrilus, 

 was filled with loosely lying spermatozoa, not compacted 

 together in any way. 



The proportions of this dilated sac to the oesophagus are 

 shown in fig. 11, which is copied from a drawing made by 

 the help of the camera lucida. The details of structure and 

 the proportions of the investing sac are more clearly shown in 

 fig. 35. 



Atria. — I term the structures in question " atria" rather 

 than " prostates^' for the reason that I have given elsewhere (4), 

 and recapitulated briefly on p. 248 of the present paper. They 

 form a pair of long tubes, which were disposed as follows in 

 my specimen. On the right side of the body the atrium, which 

 opens, as already stated, on to the 17th segment, passed straight 

 back as far as the 24th segment ; it was then sharply bent 

 back upon itself, and again reached the 17th segment, where it 

 ended blindly. On the left side the atrium was entirely con- 

 tained within the 17th, 18th, and 19th segments, being much 

 folded (fig. 18). 



A dissection of the worm did not show any difi*erentiation of 



