February 18, 1898.] 



SGLENGE. 



251 



SOCIETIES AND ACADEMIES. 

 BOSTON SOCIETY OF NATURAL HISTORY. 



The Society met January 19th, thirty persons 

 present. 



Dr. G. H. Parker described a double-mouthed 

 Metridium marginatum. The characters and the 

 two types of internal structure shown in the 

 normal form were described and compared with 

 M. (ZiaMi?!Ms and allied species. Specimens with 

 two discs were estimated to occur one in 700. 

 The habits of the young were noted, and a de- 

 tailed description of the two-mouthed specimen 

 given. Fission probably takes place in the 

 young specimen ; both oesophageal tubes are 

 entirely distinct ; all but one pair of mesenteries 

 are non-directive ; division takes place through 

 the endocoels ; longitudinal fission, through the 

 later stages, was considered probable. 



Mr. B. H. Van Vleck said that he had found 

 specimens of Metridium with two discs rather 

 more frequently than Dr. Parker's experience 

 indicated ; he had seen, perhaps, 12 or 15, and 

 considered their numerical proportion about 

 one in 200 or 300. 



Mr. Gr. M. Winslow spoke of an abnormal 

 Amblystoma. The embryo showed a supernu- 

 merary joint behind and below the left hind leg ; 

 the abnormal cartilages are separate from the 

 normal cartilages ; the muscles were described ; 

 the alimentary canal has a number of blind 

 tubules; the arteries are contracted ; the veins 

 can be traced. The abnormal pelvic girdle is 

 closest to the 14th vertebra. 



Professor C. S. Minot discussed the morphol- 

 ogy of the true kidney. In vertebrates there are 

 three distinct organs called kidney, the head 

 kidney, the middle kidney and the true kidney ; 

 two of these may occur in the life-history of a 

 single vertebrate. In structure the three differ 

 at all periods. There are two views concern- 

 ing the development of the true kidney ; it may 

 be due to embryonic connective-tissue, or to an 

 actual outgrowth of the walls of the duct ; in 

 the pig the evidence obtained is not conclusive. 

 The true kidney is fundamentally different 

 from its predecessor; the head and middle 

 kidneys are without capillary organs ; they may 

 be placed in one class, and the true kidney 

 separated into another class. Dr. Minot drew 

 attention to the specimens illustrating his 



studies, and also to a preparation showing a 

 symmetrical picture of the optic nerve of Pime- 

 lodus. 



Dr. Parker showed an embryo kitten pre- 

 pared to show the centers of ossification ; after 

 removing the viscera, the specimen had been 

 subjected to alcohol, potash, water and glycer- 

 ine. Samuel Henshaw, 



Secretary. 



PHILOSOPHICAL SOCIETY OF WASHINGTON. 



The 479th meeting of the Society was held Sat- 

 urday evening, February 5th. The first address 

 was by Professor H. W. Wiley on ' Useful Bac- 

 teria. ' Professor Wiley said in substance : In 

 one sense nearly all bacteria may be regarded as 

 useful. The following remarks, however, ap- 

 ply to those which are useful in agriculture. 

 The growing of our crops depends upon the 

 activity of bacteria in the soil. Especially is 

 this true in respect of their supply of nitroge- 

 nous food. The higher vegetables, as a rule, eat 

 only nitric nitrogen, while the original condi- 

 tions in which nitrogen enters the soil is largely 

 in an organic form, totally unsuited to nourish 

 plants. The nitro-organisms, which are the 

 cooks and prepare the food of plants, belong to 

 three classes : First, those bacteria, molds and 

 yeasts which act upon organic nitrogenous mat- 

 ter and convert it into ammonia ; second, 

 those bacteria which act upon ammonia and 

 convert it into nitrous acid ; and third, the bac- 

 teria which convert the nitrous into nitric acid. 

 The soil also contains ferments which are capa- 

 ble of oxidizing the free nitrogen of the air and 

 converting it into forms suitable for plant food. 

 It has been supposed that these bacteria live 

 chiefly in symbiosis with leguminous plants and 

 in nodules which are found on their roots. It 

 is probable, however, that leguminous plants 

 furnish simply the most favorable environment 

 for the growth of these bacteria and that they 

 may be able to convert free nitrogen into nitric 

 acid entirely independent of other plant life. 

 It may be, however, that there are two classes 

 of organisms of this kind, one oxydizing free 

 nitrogen in symbiosis and the other independ- 

 ently. Advantage is taken of this character of 

 bacteria to cultivate them in a pure state and 

 supply them in small bottles for fertilizing pur- 



