On the Nervous System of Actinia. 65 



diagram for the argument. It is a matter of fad. Focus, clear 

 = 0-10", angle 60^ + . Obviously the outside rays of this cone can 

 be traced from behind the front to its inevitable focus in front. But, 

 if considered requisite, a back and middle appropriate shall be given. 



P.S. — I have rigged tv?o semicircles divided for degrees to the 

 bottom of my zinc stage, with a shutter between, movable through 

 180"* of arc. The object-slide is also held and moved against the 

 lower surface of the stage. The very least and last light admitted 

 - by the shutter to impinge on the face of the slide gives an image of 

 the object, — with the choked, and smothered, and scouted ^-inch 

 objective. 



[It appears to us that a simple question is now involved in a needless mass of 

 phraseology. Mr. Tolles objects to the measurement described by Mr. Wenham 

 having been taken at the closed point, always considered that of greatest aperture. 

 If this is a mistake it may surely be tested. We have no doubt that Mr. Crisp 

 ■will permit the apertures of the ^th to be measured at any other position of the 

 adjusting collar that Mr. Tolles may suggest. — Ed. ' M. M. J.'] 



III. — On the Nervous System of Actinia. 



By Professor P. Martin Duncan, M.B. Lond., F.E.S., &c. 



Plates LXIX. and LXX. 



I. A Notice of the Investigations of Homard, Haime, Schneider, 

 and Botteken, and others on the subject. 



MM. Milne-Edwards and Jules Haime* wrote as follows in 1857 

 concerning the nervous attributes of the group of Coelenterata 

 called Zoantharia : — " They (les Coralhaires) enjoy a highly deve- 



DESCKIPTION OF THE PLATES. 



Plate LXIX. 



Fig. 1, which is an outline of a chromatophore, with two small ones close to it, is 

 magnified 10 diameters ; all the rest are drawn from nature under 

 the magnifying power of a J^-inch immersion lens and a medium eye- 

 piece. 



,, 2. — Bacilli. 



„ 3. — Granular and cellular protoplasm between bacilli. 



„ 4. — Large refractile cells. Haimean bodies. 



„ 5. — Type a of a Kotteken body. 



)> ". „ p ,, „ 



„ 7. — „ 7 „ „ with a thread. 



^^ 8. — Granular and cellular tissue between the Haimean bodies. 



„ 9. — Same kind of tissue in contact with a Eotteken body. 



„ 10. — Some cells with refractile nuclei in the tissue. 



J, II.. — ^Portion of tissue from amongst the Kotteken bodies, 



„ 14. — The same, with a forked end. [Fig. 12. 



* 'Hist. Nat. des Coralliaires,' vol. i., p. II. 



