l888.] NEW-YORK MICROSCOPICAL SOCIETY. 153 



3. Eudendrium ramosu7n, L. {Ccelenierata) : by L. Riederer. 



4. Pinna of Fern, Trichomafies lucens: by E. B. Grove. 



5. Radula of Crepidula fornicata, Lam.: by J. L. Zabriskie. 



6. Pollen, on anther and stigma of Abntilon roseum: by 

 Frank Healy. 



7. Pollen, on anther and stigma of Althcea officinalis : by 

 Frank Healy. 



• 8. Skin of Chameleon : by J. D. Hyatt. 



9. Section of Fossil Coral (Siliceous): by J. D. Hyatt. 



10. Section of Fossil Wood (Siliceous): by J. D. Hyatt. 



11. Fleurosigma angulatu?n, by oblique light: by E. J. 

 Wright. 



hydromedus^. 



Mr. L. Riederer, in explanation of his exhibit, read the fol- 

 lowing note : 



Tubularia la?ynx, L. and Eudendrium ramosum, L. are two 

 HydromeduscF. They belong to the Coelenterata, or Zoophyta. 

 The Hydromedusie are marine ; only one of them. Hydra, lives 

 in fresh water. The single animal forms a cup, fastened by one 

 end to a stem ; at the other end is a mouth-opening, surround- 

 ed by retractile tentacles, numbering four, six, or their multiples. 

 The mouth opens directly into the stomach, or gastrovascular 

 space. By a tube through the stem, filled by the food-juice for 

 the entire colony, there is a communication between all the 

 animals on one stem. 



"The animal consists of two distinct layers of cellular tissue; 

 the inner, or endoderm, and the outer, or ectoderm. On the 

 distal parts of the tentacles there are found, in large num- 

 bers, cells, or nematocysts, furnished with nettles, or stinging 

 threads. The slightest touch causes these cells to burst, and 

 the fine threads contained in them are forcibly thrown out. By 

 this means small animals, their principal food, are paralyzed and 

 killed. Some of the larger species of Cadenterata give rise to a 

 painful nettle-rash, when their tentacles come in contact with 

 the human skin. 



" Some animals of this family have highly differentiated cells, 

 acting as sensories for feeling, hearing and seeing. 



" The single polypes on one stem are not always similar. 



