32 F. W. GAMBLE AND J. H. ASHWORTH. 



as in fig. 34. The ripe spermatozoa closely resemble those 

 of A. Grubii, which have been accurately figured by Claparede.^ 

 They measure "058 mm. in lengthy and possess a curiously 

 shaped head/004 mm. in length, and an extremely long slender 

 tail ('054 mm. long). The head (figs. 28 and 29) is divisible 

 into three regions, — a rounded disc-like cap {S.) at the anterior 

 end, which is partially divided by a median groove ; the nucleus 

 {N.), which is large and oval in shape; and the " middle piece " 

 (M.), which bears posteriorly a depression into which the tail 

 is inserted. This depression is formed only at the time when 

 the spermatozoa are fully ripe. The tail {T.) in the specimens 

 which we have been able to obtain appeared to be a somewhat 

 stiff filament, which could only be bent to a comparatively 

 small extent. 



The breeding season of the " Laminarian" variety of Are- 

 uicola marina lasts from February to May on the Lancashire 

 coast. The large black " worms " which may be dug out 

 during the great spring tides of these months are then dis- 

 tended with ova or spermatozoa. Males and females are not 

 distinguished by external characters, but owing to the slight 

 discharge of gonads from the nephridiopores consequent on 

 the tense condition of the body, it is often possible to distin- 

 guish the sex of an example without dissection. It is at 

 present impossible to state how long these Arenicola live 

 and how many times they breed. ♦ 



The ordinary littoral lugworms of the Lancashire coast and 

 of the Isle of Man are not mature in the spring, and contain 

 at most a few very small eggs. In the summer (August) of 

 1896 we found mature specimens, and we believe that this 

 variety breeds through the summer, commencing at about the 

 time when the deeper water form has ceased. 



Relation of the Nephridia to the Reproductive 

 System. — As is well known, the ova and spermatozoa escape 

 by the nephridiopores, but it does not seem to have been noticed 

 before, that in both males and females the bladders of the last 

 five pairs of nephridia are specially enlarged (PI. 3, fig. 15, BL), 

 1 ' Aunelides de Naples,' 1868, pi. xix, fig. 2, C. 



