TRANSACTIONS OF SECTION D. — DEPT. ANATOMY AND PHYSIOLOGY. 575 



4. Oil the Nature of the ' Telson ' and ' Caudal Furca ' of the Crustacea. 



By Dr. M. M. Hartog. 



The aiithor gave a short account of tlie different views held on the nature 

 of these parts. His own explanation of them is as follows : In Copppoda the 

 anus is a terminal-dorsal slit ; the tergum of the last segment (which is prolonged 

 into the furcal process on either side the anus) is produced into a semicircular plate, 

 overhanging the anus, Avhichmay hence be termed the 'supra-anal plate.' 



Last nbd. segment. 



Supra anal plate. 



Amis. 



-d-vi 



Furcal processes. 



If this plate is produced further and becomes more or less adnate to the furcal 

 processes, the anus is pushed down thereby, becoming, tirst, terminal-ventral {e.f;. 

 phyllosoma larva of Palinurus), and then truly ventral. In the Astaeus, &c., the 

 furcal processes are visible as lateral truncate setose knobs projecting at the sides of 

 the telson a little posterior to the anus. 



Embryology also confirms the view taken that the telson of the higher Crustacea 

 is equivalent to the last ser/mmt of the nauplius bodi/, tot/ether loith an immensehi 

 developed post-anal portioJi comjioscd in vnryiiif/ prajjoiiions of the supra-anal plate, 

 and the adnate furcal processes. 



The furcal processes are regarded as outgrowths of this somite, not strictly com- 

 parable to limbs, but rather to those primitive jyaired outp-owths of the body-segments 

 ivhich have become limbs elsewhere by the development of basal articulations and a proper 

 7nusculature, specialisations which are unneeded in this segment attached only at its 

 anterior end. 



SATURDAY, AUGUST 26. 



The Department did not meet. 



MONDA Y, A UG UST 28. 



The following Papers were read : — 



1. On the Perception of Colour in Man and the Loiver Animals. 

 By J. D. Macdonald, M.D., F.B.S. 



2. An improved Method of directly determining the Velocity of the Con- 

 iraction-Wave in Curarised Muscle. By Professor E. A. Schafek, F.B.S. 



The method here briefly described is a modification of the one which was 

 originally employed by Aeby. This, which was not only the first, but still remains 

 the only direct mode of determining the velocity of the contraction-wave, consists 

 in resting upon the muscle at a carefully measured distance from one another, two 



