16 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



west of the Breakwater, and these were continued until 

 the first week in July. They demonstrated, probably for 

 the first time in the Irish Sea, the length of the period of 

 the vernal diatom maximum, which this year extended 

 to May 24th. 



" My other work dealt with the minute histology of 

 the eye of Pecten, and a study of the visceral ganglion 

 and the innervation of the osphradium in the Lamelli- 

 branchiata. The former research is being published in 

 the Quarterly Journal of Microscopical Science, and a 

 preliminary communication on the latter will be given 

 here. Representatives of twelve genera belonging to nine 

 sub-orders have been examined, and the course of the 

 osphradial nerves has been traced by the method of 

 serial sections. In several recent text-books, statements 

 have been made, based apparently on a short paper of 

 Pelseneer's, that the osphradium is innervated by the 

 cerebral ganglion. Thus in the volume on the Mollusca 

 in Ray Lankester's ' Treatise on Zoology,' we have ' The 

 osphradial ganglion receives nerve fibre not from the 

 visceral ganglion, but from the cerebral ganglion by way 

 of the visceral commissure.' A similar statement occurs 

 in Lang's ' Comparative Anatomy.' I find that in all the 

 species examined, the osphradial nerve fibres arise from 

 the branchial nerve, which takes its origin in the visceral 

 ganglion, except in the case of Pecten maximus, where, in 

 addition to this, two distinct nerves can be traced directly 

 from the ganglion. No nerve fibres leave the cerebrovisceral 

 connectives for the direct innervation of the osphradium. 



" During the examination of some of these lamelli- 

 branchs, the remarkable Nemertean Malacobdellu was 

 discovered in the pallia! cavity of Venus casina, and also 

 in My a truncata from Piel. The usual host is Cyprina 

 islandica, but I am not aware of any previous records of 



