NATURAL SCIENCES OF PHILADELPHIA, 89 



our pavements many individuals of the common wheel-animalcule, 

 liotifer vulgaris^ he had made some observations relating to the 

 assertion that the}' might be revivified on moistening them after 

 they had been dried up. 



Two glass slides, containing, beneath cover glasses, some dirt, 

 exhibited each about a dozen active living Rotifers. The glass 

 slides were placed, on a window ledge of my study, the thermo- 

 meter standing at 80. In the course of lialf an hour the water 

 on the slides was dried up and the dirt collected in ridges. The 

 next morning, about twelve hours after drying the slides, they 

 were placed beneath the microscope. Water was applied and the 

 materials on the slides closely examined. On each slide a number 

 of apparently dried Rotifers were observed. Tliese imbibed 

 water and expanded, and some of them in the course of half an 

 hour revived and exhibited their usual movements, but others 

 remained motionless to the last. 



The same slides were again submitted to drying, and from one 

 of them the cover glass was removed. They were examined the 

 next day, but several hours after moistening them only two 

 Rotifers were noticed moving on each slide. 



I next prepared a slide on which there were upwards of twent}' 

 actively moving Rotifers, and exposed it to the hot sun during 

 the afternoon. On examination of the slide the following morn- 

 ing, after moistening the material, all the Rotifers continued mo- 

 tionless, and remained so to the last moment. 



From these observations it would appear that the Rotifers and 

 their associates became inactive in comparatively dry positions 

 and may be revived on supplying them with more moisture, but 

 w^hen the animals are actually dried they are incapable of being 

 revivified. Moisture adheres tenaciously to earth, and Rotifers 

 may rest in the earth, like the Lepidosiren, until returning waters 

 restore them to activit3^ 



Prof. Cope mentioned the capture of a young Balsena cisarctica^ 

 of fort3'-eight feet in length, in the Raritan River, near South 

 Amboy, on May 30th. The skeleton was buried and would be 

 preserved in some museum. He examined the whalebone, of 

 which there are 245 laminae on each side of the mouth. The color 

 is black and the hair is fine, long, and has a brownish tinge ; length 

 of longest plate with hair, 48 inches. The gum is 11 G inches long 

 and 11 inches deep. He was informed that the whale was entirely 

 black, and the dorsal line without irregularities. 



Prof. Cope exhibited mounted crania of some gigantic horned 

 mammalia of the Miocene of Colorado, viz., the Symhorodon 

 bucco, S. aUirostris, S. acer, and S. tHgonoceros. He explained 

 the distinctive features of this genus as compared with Titaiio- 

 therium, exhibiting typical specimens of the latter from the Aca- 

 demy's museum, showing four inferior incisor teeth, while the 

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