No. 634] SHORTER ARTICLES AND DISCUSSION 453 



so difficult to study on account of the problem of proper technic 

 that it is not surprising that many incomplete descriptions should 

 have been published. It is to be hoped, however, that the day 

 will come when nematodes will be as thoroughly studied and de- 

 scribed as other parasitic worms have been and that their classi- 

 fication and identification will be made more certain. 



Thomas Byrd Magath 



Mayo Clinic, 



BIBLIOGRAPHY 



Leidy, J. 



1851. Contributions to Helminthology. Proc. Acad. Nat. Sci., V, 239- 



MacCallum, G. A. 



1918. Notes on the Genus Camallanus and other Nematodes from Vari- 



ous Hosts. Zoopathologica, I, 123-134. 

 Magath, T. B. 



1919. Camallanus americanus nov. spec. Tr. Am. Microsc. Soc, 



XXXVIII, 49-170. 

 Ward, H. B. 



1917. On the Structure and Classification of North American Parasitic 



Worms. Jour. Parasitology, IV, 1-12. 

 Ward, H. B., and Magath, T. B. 

 1917. Notes on Some Nematodes from Fresh-water Fishes. Jour. 



Parasitology, III, 57-64. 



AN AMICRONUCLEATE EACE OF PARAMECIUM 

 CAUDATUM 



Probably no representative of the Protozoa has received more 

 attention in matters relating to life cycles, reproduction, hered- 

 ity and cytology than has Paramecium. It should be of general 

 interest, therefore, to record the occurrence of a race of Para- 

 mecium caudatum which appears to be entirely devoid of a 

 micronucleus. The recent studies by Dawson (1) on an amicro- 

 nucleate race or species of Oxytrklia add interest to the present 

 discovery. 



In the fall of 1914 Doctor M. H. Jacobs of this Laboratory 

 used, in certain heat experiments, some Paramecium caudatum 

 derived from a culture which exhibited great viability. During 

 the following January Hance (2), in examining some of the sur- 



