I 82 MAX MORSE. 



studied the histological changes occurring in Hydra subjected to 

 reduced temperatures and is unable to corroborate Greely, but 

 rather shows that a loss of water accompanies the lowering of 

 the temperature, which causes the hydroids to become opaque, 

 without degenerative changes in the cells. 



Little success has been had with Tubularia in exhibition tanks. 

 If some means could be devised for keeping the water in such 

 tanks at a temperature, say of 15 C., the writer believes that 

 Tubularia could be maintained in health, as in the sea. 



The writer has studied Tubularia at the Bureau of Fisheries 

 and the Marine Biological Laboratory, at Woods Hole and at 

 the Harpswell Laboratory. To those in charge of these labo- 

 ratories, Professors Sumner, Lillie and Neal and to Dr. Kingsley 

 and Professor Lambert, the writer is indebted for much kind- 

 ness. The work was started at the suggestion of Dr. T. H. 

 Morgan and the writer is grateful to him for generous aid and 

 criticism. 



COLLEGE OF THE CITY OF NEW YORK, 

 December 15, 1908. 



