1887.] NATURAL SCIENCES OF PHILADELPHIA. 235 



fore only been found in his original locality, the rock water-tanks of 

 Bombay, East Indies. That it should skip a whole hemisi^here and 

 only be found the second time at its own antipodes is indeed re- 

 markable. 



The lower reaches of the Colorado of the West extend for miles 

 through a region described by the collector as "the hottest, driest, 

 and most barren in the United States," whose "vegetation consists of 

 mesquit, cacti, and the screw-bean, Strombocarpus pxibescens." Its 

 normal border lands are known as the "first" and "second bot- 

 toms," of which the latter are the higher and of course more distant 

 from the channel. By the frequent changes in its bed however, 

 the river cuts through these and, washing away the one and filling 

 up the other, reverses their physical conditions. Upon the "second 

 bottoms" then, said to be only reached to any considerable depth 

 by the annual floods occurring during parts of May and June, 

 and not to continue flooded more than six weeks at a time, the 

 screw-bean abounds. It is described as a small tree of the general 

 appearance of a peach tree, but with more slender, drooping branches. 

 More or less of an alkaline deposit whitens the ground uj)ou which 

 they grow, and the approaching traveler is puzzled to see in strong 

 contrast with it, hundreds or even thousands of dark masses, "like 

 wasp's nests," suspended two or three feet above. 



It was this conundrum that confronted Dr. Palmer during his 

 recent visit, and the answer we have in the sponge before us. From 

 the Amazon River in the tropics to the waters of Maine and Nova 

 Scotia in the temperate regions of the north, sponges have long been 

 kno^vn to affect the pendent branches of stream-bordering bushes ; 

 but it is unlikely that they have ever before been observed in such 

 quantities suspended for nine or ten months of the year over land 

 parched and desolate. 



On referring to the earlier descriptions of his discoveries, by H. J. 

 Carter, we find that though he collected this species on two or 

 more occasions, the fragments were always found detached from 

 their place of growth and floating upon the surface in the 

 water-tanks referred to, about one month after the rainy season 

 had commenced. He believed that the vitality of the gemmules 

 was preserved during the diy season, notwithstanding their expos- 

 ure to the sun and desiccating winds, and that their germination 

 after the water had again reached them was followed by a very rapid 

 growth of new sponge. This would seem to have been the case also 



