2362 Journal of Applied Microscopy 



are very easily performed, and if plenty of clear water surrounds the cut pieces 

 of Planaria they will almost invariably be successful. 



B. As a morphological type. 



Planarians are comparatively simply organized Metazoa, and are representa- 

 tives of the simplest worms. They are well adapted for study as a morpholog- 

 ical type form, wherever a compound microscope is available. They have 

 represented in the simplest condition all the organ systems — nervous, digestive, 

 reproductive, excretory, etc., — found in the higher worms, such as for example 

 the earthworm. 



C. To demonstrate reproduction by fission in a metazoan. 



Many planarians regularly reproduce asexually by transverse fission. If 

 specimens are isolated under favorable conditions they will be found to divide 

 transversely. In these products of fission the missing parts are subsequently 

 regenerated. 



Other uses, besides these suggested here, to which planarians may be put in 

 teaching work will readily occur to teachers who have them in the laboratory. 



(4) Readily Accessible Life?-atiire dealing zoifli Planarians. 



Excellent accounts of the anatomy, habits, methods of reproduction, distri- 

 bution and taxonomy of planarians are to be found in : 



1. The Cambridge Natural History. Volume II. New York (The Mac- 

 millan Company), 1896. Price, $3.50 net. 



The part of this volume dealing with planarians is contributed by Gamble, 

 and is probably the best general account of these forms in existence. 



2. Parker, T. J., and Haswell, W. A. A Text-book of Zoology. 2 Vols. 

 New York (The Macmillan Company). 1899. Price, $9.00. 



A very good account of the biology of planarians is included in the first vol- 

 ume of this work. 



The following works deal with special topics regarding planarians : 



1. Morgan, T. H. Regeneration. New York (The Macmillan Company). 

 1901. (Columbia University Biological Series, vii.) Price, $3.00. 



In this work is summarized practically all that is known regarding regenera- 

 tion in planarians. Anyone interested in this subject should consult this work. 



2. Pearl, R. The Movements and Reactions of Fresh Water Planarians ; 

 A Study in Animal Behavior. Quarterly Journal of Microscopical Science. N. 

 S., Vol. 46, pp. 509-714, 1903. 



Discusses the habits and behavior of planarians. 



3. Curtis, W. C. The Life History, the Normal Fission and the Reproduc- 

 tive Organs of Planaria maculata. Proceedings of the Boston Society of Nat- 

 ural History. Vol. 30, No. 7, pp. 515-550, pi. 9-19, 1902. 



Discusses the methods of reproduction in Planaria. 

 University of Michigan. RAYMOND Pearl. 



