54 Prof. M'lntosh's Notes from the 



each side. In the middle of the body the nerve-cords are 

 still separated by a considerable intcrval_, the median mesen- 

 tery Avitli the ventral vessel being attached to the basement- 

 tissne between them, and each has a large nenral canal tilled 

 with coagnlable snbstance superiorly — occujiying fully half 

 the area. Instead of the more or less complete fusion of 

 the ganglia at intervals, all that occurs in this type is a slight 

 increase of the nerve-cells in the separate trunks and the 

 passage of commissural fibres between thcni, with an increase 

 of the neuroglia and its nuclei, the large neural canals under- 

 going no change. The iuterganglionic regions are recog- 

 nized by the absence of the transverse or commissural fibres 

 and of the increased neuroglia, and by the conspicuous 

 condition of the median ventral mesentery with its hlood- 

 vessel, the strands of the mesentery passing directly to the 

 basement-tissue. 



Posteriorly the great nerve-cords are nearer eacli other, 

 yet separated by a considerable interval. In section they 

 have the same granular and streaked appearance, with a 

 small neural canal at the upper and outer border, which lies 

 against the inner margin of the ventral muscle. Numerous 

 neuroglial nuclei occur at the commissural regions, which 

 occur as in front. In longitudinal sections of the tail the 

 nerve-cords follow every fold of the body-wall, dipping with 

 a sharp angle into each pit, so that the neural canals have no 

 noteworthy influence in this connection. The main direction 

 of the nerve-fibres is longitudinal, and lateral branches leave 

 at each dissepiment even to the tip of the tail. 



Various authors have dealt with the general topography 

 of the nervous system of the Serpulids : the earlier, such as 

 De Quatrefages, described a smaller and a larger pair of 

 cephalic ganglia which lie over the oesophagus, with the 

 various nerves which proceed from them. Pruvot also held 

 that there were two pairs of ganglia. E. Meyer, again, 

 found that in Psygmobranchus protensus and Eupomatus 

 lunuliferus, Clap., there were, in addition to the smaller 

 central and the larger lateral lobes from which the great 

 trunks to the branchial system arise, two accessory lobes to 

 the latter ; and his minute account of the branches from 

 the cephalic ganglia and of those from the great nerve-cords 

 (termed by him " spinal nerves ") is excellent and his figures 

 carefully drawn. 



Reproduction. — In the ripe female, longitudinal sections 

 of the tip of the tail show that the larger ova in the coelomic 

 spaces do not, as a rule, extend quite to the tip, about eight 



