1876.] On Thallophytes parasitic within Madreporaria. 17 



May II, 1876. 



Dr. GUNTHER, M.A., Vice-President, in the Chair. 



The Presents received were laid on the table, and thanks ordered for 

 them. 



The following Papers were read : — 



I. On some Thallophytes parasitic within recent Madre- 

 poraria.'' By P. M. Duncan, M.B., F.B.S., President of the 

 Geological Society. Received March 17, 1876. 



(Abstract.) 



After noticing the works of Quekett, J. P. Rose, Wedl, and Kolliker 

 on the filament-shaped parasites within recent and fossil molluscan shells 

 and scales, and his own researches into and descriptions of correspond- 

 ing growths in Madreporaria from the Silurian and Tertiary rocks, 

 the author proceeds to explain the method of investigation employed in 

 the examination of recent corals. The range of the parasites is then 

 stated to be, in corals from the littoral zone down to 1095 fathoms, 

 and from Davis Straits to the tropical coral seas, and their lowest known 

 temperature habitat is that of 31°-5 Fahr. 



A list of species examined is given, and then the long slender canals 

 with their included filamentous organisms are described. Then the 

 method of entry of the growth is stated, and its relation to the organic 

 basis of the coral sclerenchyma is explained. The reproduction by conidia 

 and oospores is also explained. After noticing that the direction, 

 branching, and size of the parasites depend upon the special pecuharities 



~% 



tion of the brain anodic closure is more effective than katliodic. This, of course, is 

 precisely the reverse of what I find to be true of muscle ; and as the fact of such a 

 diflFerence existing between the two cases is very remarkable, I may observe that it 

 appears to confirm Hitzig's views concerning the reversed relations that subsist between 

 central and peripheral galvanic stimulation. 



I may also observe that I have repeatedly tried whether there is any difference to 

 be detected between anodic and kathodic closure in the case of motor nerves, but 

 hitherto without success. Yet, as it seemed to me very improbable that there should 

 be any difference between nerve and muscle in this respect, I had intended to investi- 

 gate the matter still further before publishing any thing with regard to nerve. I now 

 find, however, that Hitzig's results with regard to brain had induced Engesser (Pfliig. 

 Arch. X. p. 157 &c.) carefully to investigate the question with regard to motor nerves ; 

 and the conclusion he arrives at is that no difference can in their case be detected 

 between the effects of anodic and of kathodic closure. Therefore, as this result agrees 

 with my ovni, it seems desirable that I should here acknowledge the agreement. No 

 one, so far as I can ascertain, has as yet published any thing in this connexion with 

 regard to muscle. — G. J. E., May 5th, 1876. 



TOL. xxy. 



