NOTES AND MEMORANDA. 131 



or pigment granules were discovered, even after the most diligent 

 search with high powers, ranging up to the ^V*^ ^^ ^^ i^ch objective, 

 in the fresh blood. This paper is of considerable length and is worth 

 reading. 



The Nervous System of Actinia. — The following is an abstract of 

 Dr. Martin Duncan's, F.K.S., paper in a late number of the ' Pro- 

 ceedings of the Eoyal Society.' After noticing the investigations of 

 previous anatomists in the histology of the chroraatophores, the work 

 of Schneider and Eotteken on these supposed organs of special sense is 

 examined and criticized. Agreeing with Eotteken in his description, 

 some further information is given respecting the nature of the 

 bacillary layer and the minute anatomy of the elongated cells called 

 " cones " by that author. The position and nature of the pigment cells 

 are pointed out, and also the peculiarities of the tissues they environ. 

 It is shown that the large refractile cells, which, according to Eotteken, 

 are situated between the bacilli and the cones, are not invariably in 

 that position, but that bacilli, cones, and cells are often found 

 separate. They are parts of the ectothelium, and when conjoined 

 enable light to affect the nervous system more readily than when they 

 are separate. Further information is given respecting the fusiform 

 nerve-cells and small fibres noticed by Eotteken in the tissue beneath 

 the cones ; and the discovery of united ganglion like cells and a 

 diffused plexiform arrangement of nerve is asserted. The probability 

 of a continuous plexus round the Actinia and beneath each chromato- 

 phore is suggested, and the physiological action of the structures in 

 relation to light is explained. The minute structure of the muscular 

 fibres and their attached fibrous tissue in the base of Actinia are 

 noticed ; and the nervous system in that region is asserted to consist 

 of a plexus beneath the endothelium, in which are fusiform cells and 

 fibres like sympathetic nerve-fibrils. Moreover, between the muscular 

 layers there is a continuation of this plexus, whose ultimate fibrils 

 pass obliquely over the muscular fibres, and either dip between or are 

 lost on them. The other parts of the Actinia are under the examina- 

 tion of the author, but their details are not sufficiently advanced for 

 publication. The nervous system, so far as it is examined, consists of 

 isolated fusiform cells with small ends (Eotteken), and of fusiform 

 and spherical cells which communicate with each other and with a 

 diffused plexus. The plexus at the base is areolar ; and its ultimate 

 fibres are swollen here and there, the whole being of a pale-grey 

 colour. 



NOTES AND MEMOEANDA. 



The Chair of Comparati-v e Embryology at the College of France. 



— The Academy, which has the right to nominate two candidates for 

 this post, held a meeting for the purpose of nomination on the 9th of 

 February. At this meeting the candidates to be recommended to the 



