NIDAMENTAL TISSUES 491 



offer obstructions that are not easily surmounted. Much can be done 

 to help this by seeing that these are removed by natural processes at 

 the time of killing the animal. The secreted material in the cells 

 themselves often makes the sections brittle and poor. 



A better appreciation of these tissues may be obtained by observing 

 them in action during the life of the animal. Linton and Curtis have 

 studied them thus in transparent worms, and much interesting work has 

 been done in this way. Such observations have been made on larger 

 animals which were not transparent, as the cephalopod mollusks, by 

 cutting out or exposing the parts in a freshly killed animal and watch- 

 ing the operations that were automatically performed until near the 

 death of the tissue, which takes place some time after that of the individ- 

 ual as a whole. 



LITERATURE 



ELLERMANN. "Uber die Schleimsekretion in Eileiter der Amphibien," Anal. Anz., 



Band XVIII, 1900. 



SCHNEIDER. " Monographies der Nematoden." Berlin, 1866. 

 ANDREWS, E. A. "Habits of the Crayfish," Johns Hopkins Univ. Circular, Vol. XIV, 



p. 74. M 

 BROCK, J. "Uber die Geschlechtorgane der Cephalopoden," Zeits.f. Wiss. Zool., Band 



XXXII, 1879. 

 LINTON, E. " Fish Parasites collected at Woods Hole in 1898," Bull, of the U. S. F. C., 



1899, pp. 267-304. 

 CURTIS, W. C. "The Life History, the Normal Fission, and the Reproductive Organs of 



Planaria maculata." Proceedings of the Boston Society of Natural History, Vol. 



XXX, No. 7, 1902. 

 WILLIAMS, L. W. An unpublished article on the anatomy of Loligo Pealii about to 



appear in the Bull, of the U. S. F. C. 



