186 



Trans-net / on s. 



ventral surface and on the right side, but on the dorsal surface and on the 

 left side it is merged into the 2nd. The 3rd segment as seen from above 

 is unsymmetrical, but owing to a wound in the skin on the dorsal surface 

 the exact course of the intersegmental furrow cannot be traced. It is 

 from the hinder face of this segment that the branch arises, on the right side 

 and nearer to the dorsal than the ventral surface. As seen from below, 

 this segment has the form usually seen in bifurcated worms — that is, its 

 posterior boundary on the right side is oblique, forming an angle of nearly 

 45° with the long axis of the body. Consequently a backwardly directed 



Fig. 1. — Outline of Lumbricus rubellus, with a branch on its right side springing 



from the clitellum. Natural size. 

 Fig. 2. — Dorsal view of the clitellar region : the dotted area represents a damaged 



portion of the skin. > 4. 

 Fig. 3. — Ventral view of the same, x 4. 



angular projection exists between the branch and the body. This angle, 

 or " axilla,"' is clearly seen ventrally, but is merged into the next segment- 

 on the dorsal surface. 



The 4th segment of the clitellum, again, is unsymmetrical, as seen from 

 above, being wider on the left and narrow on the right side, just below 

 the axilla. 



The remaining segments, 5, 6, and 7, are normal. It is usually the case 

 in these bifurcated worms that some segments are abnormally and irregu- 

 larly developed. 



Traces of the tubercula pubertatis are present in the form of a slight 

 ridge on each side of the 3rd, 4th, 5th, and 6th segments, at the line where 

 the glandular epidermis ceases latero-ventrallv. 



The branch thus springs from the 3rd clitellar segment ; and the following 

 three segments that form its base are also glandular — that is to say, the 

 clitellum is continued on to the branch, and the ridge (or tubercula puber- 

 tatis) is continued along the outer side of these three segments. 



The body is 73 mm. in length, with a diameter of about 4 mm. just 

 behind the clitellum ; the branch measures 14 mm. by 1-75 mm., and arises, 

 as the figure shows, at a point about 18 mm. from the anterior end. It 

 contains 15 segments, mostly biannulate, as on the body of the worm. 



The chaetae on the body are, of course, in four couples, the individuals 

 of a couple being close together ; but the only chaetae that I can detect 



