proceedings: biological society 309 



Paul Bartsch: Oh;- poison gas detector and how it was discovered. 

 (Illustrated). 



Dr. Bartsch first described the nocturnal mating habits of Limax 

 maximiis, a common garden slug, illustrating the successive acts with 

 photographs taken by flash-light. The slugs, which are bi-sexual, 

 climb trees at night; a pair will twist themselves together, spin a mucous 

 thread, and hang suspended. The genitalia are protruded, and after 

 exchange of products, accompanied by characteristic activities, the 

 pair ascend the thread and retire to their usual retreats where the eggs 

 are deposited. 



Some vears ago, Dr. Bartsch continued, a number of aninfals of this 

 species which were under observation in his home, escaped from their 

 box in which they had been confined. Observations on their behavior 

 in the furnace room were recalled when need for a gas detector arose in 

 connection with the great war. A very brief period of experimentation 

 revealed the extraordinary sensitiveness of Limax maximus to mustard 

 gas, and in an incredibly short time the information, invaluable for 

 detecting the gas, was in the hands of the Allies and American forces 

 in Europe. The tentacles of Limax are sensitive to a dilution of i to 

 10,000,000 of mustard gas, and characteristic responses indicate the 

 degree of dilution. vSince man reacts at a dilution of i to 4,000,000, 

 Limax proves to have ample margin of delicacy. Moreover the species 

 is European, and. abundant in the region of the fighting. 



Dr. Bartsch pointed out how incidental, even accidental, observations 

 years ago furnished immediate answer to the problem calling for reliable 

 sensitive detectors of certain gases during the war. 



The paper was discussed by Dr. H. M. vSmith. 



607TH MEETING 



The 607th meeting of the Biological Society of Washington was held 

 jointly with the Washington Academy of vSciences in the lecture hall 

 of the Cosmos Club at 8.15 p.m., February 21, 1920. President Hop- 

 kins presided, and 75 persons were present. 



Upon recommendation of the Council, Miss Doris Lang worthy, of 

 George Washington University; Mr. K. P. Schmidt, of the American 

 Museum of Natural History, and Miss Marion Pellew, were elected 

 to membership. 



The address of the evening was given by Dr. Alfred G. Mayor, 

 Director of the Division of Marine Biology, Carnegie Institution of 

 Washington, and Lecturer in Zoology at Princeton LTniversity, upon 

 the subject: The coral reefs of American Samoa. 



The Island of Tutuila in its relation to its marine environment was 

 described, and the distribution of the various reef -forming algae and 

 corals. The island is very old as is shown by geological evidence. The 

 reefs were described, including rate of coral growth, and the conditions 

 prevailing, and the various theories of reef formation were discussed 

 in the light of the observations made at Tutuila. Though none of these 



