ON DREPANIDOT-^NIA HEMIGNATHT. 617 



the appearance of a well-marked double line, which is very 

 characteristic, and is well shown in fig. 6. 



Scattered amongst the parenchyma are certain faintly stained 

 cells which seem to be bipolar, and which differ from the cells 

 of the parenchyma both in shape and in their powers of 

 absorbing the staining reagents. These I take to be nerve- 

 cells which are in communication with the nerve fibres of the 

 lateral cords. The latter are entirely devoid of any nerve- 

 cells on their course. 



Muscle-fibres are scattered through the substance of the 

 body, and one set of longitudinal muscles are most definitely 

 arranged. This layer is situated just below the epidermis in 

 the anterior part of the segment, but as the latter increases in 

 size posteriorly, the cylinder of muscle-fibres, which retains 

 the same diameter throughout, comes to lie more deeply in 

 the tissues. These muscles, like the nervous system and ex- 

 cretory canals, run from segment to segment; some of them, 

 if not all^ end in the cuticle, where it is most bent in at the 

 posterior end of each segment. Laterally the fibres are not 

 in contact, being separated by considerable intervals. Their 

 regular arrangement is shown in fig. 6. 



In the posterior segments, which are so ripe that the slightest 

 touch breaks them off, the parenchyma has undergone con- 

 siderable degeneration, the cells are less clear^ and the spaces 

 of the meshwork are larger and more irregular. 



The generative organs begin to arise very early in the series 

 of segments. Already in the eighth or tenth segment clusters 

 of cells are segregating, and their deep staining shows that 

 they belong to the gonads. In the sexually ripe segments the 

 ovary is centrally placed, and is supported on each side by a 

 lobe of the testis. From the latter a fine vas deferens leads 

 into an extensive vesicula seminalis, which is as a rule crowded 

 with spermatozoa; from this a muscular duct leads to the 

 unilateral genital pore. I was unable to make out the details 

 of the penis, and similarly I failed to detect any yolk-gland 

 amongst the female genitalia. 



The vagina leads at once into a large receptaculum seminis. 



