Maech 21, 1902.] 



SCIENCE. 



All 



two elements, the indigenous forms which 

 were developed in that continent, and the im- 

 migrants from other regions. In South 

 America this distinction is easy to draw, be- 

 cause of the remarkable series of Tertiary 

 deposits which are wonderfully rich in well- 

 preserved fossils. The Santa Cruz beds, 

 which are almost certainly referable to the 

 lower Miocene, contain an assemblage of 

 mammals altogether different from those of 

 the northern hemisphere. The fauna consists 

 of Primates and Insectivora, very scantily 

 represented, very numerous Eodents (though 

 all referable to the Hystricomorphs), Mar- 

 supials, Edentates and the peculiar South 

 American hoofed animals. The Edentates of 

 this period represent the Gravigrada, Gljrp- 

 todonts and Armadillos, but no members 

 of the true Sloths or Anteaters have yet been 

 found, a lack of which is probably due to 

 climatic conditions. The Gravigrada, which 

 are very abundant, have forerunners of all the 

 great Pleistocene groups, but are, of course, 

 much less specialized and are relatively small 

 in size. The Glyptodonts, though numerous 

 and well preserved, are not so easily to be 

 brought into relation with the later genera of 

 the same group. 



The paper concluded with a brief examina- 

 tion of the remarkable Ungulates, all of which 

 are peculiar to South America, and especial 

 attention was called to Ameghino's discovery, 

 yet unpublished, that in Nesodon there are 

 three sets of functional incisors and canines. 

 Incredible as such an observation may be, it 

 seems to be well established. 



Henry E. Crampton, 



Secretary. 



THE BOSTON SOCIETY OP NATURAL HISTORY. 



At a meeting of the Society held January 

 1, 1902, Dr. George H. Parker gave an ac- 

 count of some experiments which he had con- 

 ducted on the marine Copepod, Lahidocera 

 osstiva, with a view to aecoimting for the fact 

 that it is extremely abundant on the surface 

 of the water along shore at night, but during 

 the hours of daylight is found only down in 

 the deeper waters. After giving a short ac- 

 count of the external structvire and method of 



locomotion, the speaker described a series of 

 experiments with these copepods in aquaria, 

 from which it appeared that the females are 

 negatively geotactic, their tendency being to 

 swim against rather than with the force of 

 gravity. They were also found to be attracted 

 by a light of small intensity, but repelled by 

 a brilliant illumination. The reactions to 

 light seem to be stronger than those to grav- 

 ity. The diurnal migration on the part of 

 the females is thus to be explained as being 

 due to their endeavor to seek a region of such 

 depth below the surface of the water as shall 

 have the requisite intensity of light. The 

 males of this species seemed to show no very 

 definite response to light or gravity, though 

 their reactions indicated that they were to 

 a slight degree negatively phototactic, and 

 positively geotactic. By experiments with 

 females enclosed in small glass tubes, which 

 were covered with filter paper and plugged at 

 the ends with cotton, it seemed evident that 

 the females give out some sort of scent which 

 becomes disseminated throughout the imme- 

 diately surrounding water, and is strongly at- 

 tractive to the males. The males, then, per- 

 form the same diurnal migration as the 

 females, because they are attracted by the 

 scent of the latter, and so follow in their 

 wake. Mr. 0. J. Maynard then gave an 

 account of the habits and structure of the 

 Anhinga and the Courlan, two Florida birds. 

 Among the specimens shown was a prepara- 

 tion of the peculiar convolution of the trachea 

 in the adult male of the latter species, a strik- 

 ing secondary sexual character. 



At the meeting of January 15, 1902, Mr. 

 WjUiam L. W. Field gave an account of a 

 '. Glacial Lake Problem in Southern Vermont.' 

 The region studied covers a portion of the 

 basins of the Black and the Williams rivers, 

 tributaries of the Connecticut. At a certain 

 locality the courses of these two rivers approx- 

 imate rather closely, and at this region there 

 are two passes connecting the respective 

 river basins, the one very narrow, with steep 

 sides, locally known as Proctorsville Gulf, the 

 other, farther down the valley, much broader 

 and apparently widened to a considerable ex- 

 tent by ice action. From a study of the sedi- 



