14-4 PROCEEDINGS OF THE ACADEMY OF 



and rise to the surface, where the}' maj- receive the influence of 

 light and air. In examining the surface-mud of a shallow rain- 

 water pool, in a recent excavation in brick clay, he found little 

 else but an abundance of minute diatomes. He was not sufficiently 

 familiar with the diatomes to name the species, but it resembled 

 Navicula radiosa. The little diatomes were very active, gliding 

 hither and thither, and knocking the quartz sand grains about. 

 Noticing the latter, he made some comparative measurements, and 

 found that the Naviculoe would move grains of sand as much as 

 twenty-five times their own superficial area, and probably fift}'^ 

 times their own bnlk and weight, or perhaps more. 



Dr. J. Gibbons Hunt made the following remarks : 



"While examining, this summer, into the structure of some of the 

 so-called insectivorous plants, but more especially' into the ana- 

 torn}' of the genus Nepenthes^ I observed a part which I have not 

 seen expressed before, and of sufficient interest, perhaps, to go 

 upon record. 



In the vegetable kingdom it is exceedingly rare to meet with 

 glands which have distinct excretory ducts. Some authors deny 

 their existence entirely; but in Nepenthes rafflesiana^ N. distilla- 

 toria, and X. 2)hyUamphora, and probabW in all the species, are 

 large C3dindrical glands which pour out their secretion through 

 distinct excretory ducts. In N. distiUatoria these glands are, on 

 an average, about the one-thirt3'-fifth of an inch long, and the 

 one-twentieth of an inch wide, while the ducts measure about the 

 one-thirtietli of an inch in length. In the Rafflesiana the glands 

 and ducts are much larger. A dense tissue of cells surrounds and 

 thoronghl}' imbeds these glands in Nepenthes.^ and this peculiarity 

 of position renders excretory ducts necessary for the secretion to 

 find its way into the pitchers. 



In the vegetable kingdom it is the rule for glands to be located 

 on surfaces, but in Nepenthes where one s^'Stem of glands is im- 

 bedded the duct becomes necessary', and so far as I know is the 

 only instance of such ducts among plants. 



September 22. 

 The President, Dr. Ruschenberger, in the chair. 

 Thirt3'-five members present. 



Remarks on Sponges. ^-Fr of. Leidy remarked that the animal 

 nature and structure of the sponges were first clearly made known 

 b}' Mr. H. J. Carter, of England, and Prof. H. James Clark, of 

 this country'. The sponges are compound, flagellate infusoria. 

 The sponge infusorium had been a])propriately named by Mr. 

 Carter the spongozoon, the exact characters of which were first 



