444 G. H. PARKER AND E. G. TITUS 



p. 528) on the alcyonarians, though the assertions of the first 

 two authors on this point have been called in question by Wolff 

 ('04, p. 257) and by Kassianow ('08 a, '08 b). From a physio- 

 logical standpoint Carpenter ('10, p. 159) has pointed out for 

 certain corals the probability of just such nervous connections 

 as have been described by Ha vet. 



In attempting an elucidation of the nervous system of Metri- 

 dium, a variety of methods were used. The isolation method, 

 as employed by the Hertwigs, yielded important confirmatory 

 results. Serial sections subjected to a variety of stains were 

 also found serviceable. By the Golgi method many of the re- 

 sults obtained by Havet were confirmed. Material was pre- 

 pared by the methylen-blue method, by the Bielschowsky, 

 the Ranson, and the Ramon y Cajal methods, but only after 

 an essentially new procedure was devised were results of im- 

 portance obtained. This method was worked out by Dr. E. G. 

 Titus and is briefly as follows: 



Small specimens of Metridium, a centimeter or less in diameter, 

 were taken directly from the sea and rinsed for a few seconds 

 in distilled water, after which they were immersed for ten minutes 

 in a 5 per cent solution of silver nitrate. The silver-nitrate 

 solution with the abundant precipitate was then poured off and 

 the specimen was again rinsed in distilled water after which it 

 was put in a fresh 5 per cent silver-nitrate solution for half an 

 hour during which the solution was once changed. It was 

 then passed quickly through graded alcohols, 30, 50, 70, and 90 

 per cent, and left for about an hour in absolute alcohol. Next 

 it was carried through a reversed series of graded alcohols to 

 distilled water in which it was washed an hour by agitation 

 and with frequent changes. From the water it was transferred 

 to a 5 per cent solution of silver nitrate in which it remained 

 five days. Then it was rinsed in distilled water and put in a 

 hydrochinon solution containing 2 grains of hydrochinon in 

 each 100 cubic centimeters of a 5 per cent solution of formalde- 

 hyde in water. Here it remained 30 hours after which it was 

 rinsed in water, dehydrated in alcohol, passed through xylol 

 to parafhne and cut into paraffine sections 10 to 15 micra thick. 



