THE 



MONTHLY MICROSCOPICAL JOURNAL, 



MAY 1, 1870. 



I. — On the Reparation of the Spines of Echinida. 

 By W. B. Cabpenter, M.D., Y.P.K.S. 



{Read before the Royal Microscopical Society, March 9, 1870.) 



Plate XLIX. 



In my 'Keport on the Microscopic Structure of Shells' com- 

 municated to the British Association in 1847, in which the first 

 detailed account was given of the structure of Echinus-spines 

 derived from the examination of transparent sections,* I described 

 and figured appearances t which seemed to me to indicate that a 

 power of reparation exists in these bodies, notwithstanding the 

 very small amount of soft tissue they contain when living, and the 

 remote connection which this has with the nutritive apparatus. I 

 further expressed the opinion that the reparation is effected by the 

 investing membrane of the spine, which appears not only to j)Ossess 

 the power of depositing new concentric layers of the calcareous 



EXPLANATION OF PLATE XLIX. 



Fig. 1. — Spine of Echinus trigonariiis, showing partial reparation at its truncated 

 extremity. 



2. — Section of a similar spine, showing the termination of the pillared 

 structure at the line of demarcation between the stump and the new 

 growth. 



3. — Section of a spine of AcrocIacUa, showing the derivation of the new 

 growth from the outer layer of the stump. 



4. — Portion of a transparent section of the same spine, through the line of 

 fracture, magnified six diameters. 



5. — Section of a spine of Echinus trigomtrius, of which the normal length 

 and shape have been almost entirely restored by a new growth. 



6. — Portion of a transparent section of a spine of Acrocladia, through the 

 line of fracture, magnified thirteen diameters ; showing the contrast 

 between the pillared structure of the stump, and the simple reticula- 

 tion of the new growth. 



* The fullest description previously given of these beautiful structures was 

 that of Professor Valentin, in his 'Monograpli on the Anatomy of the Genus 

 Echinus.' Neuchatel, 1842. 



f Loc. cit., § 115, Fig. 65, dd, ee. 

 VOL. III. Q 



