268 



SCIENCE 



[N. S. YoL. XXXVII. No. 946 



of Jacobson is wanting. Seydel assumed that this 

 simple condition of the olfactory organ of Neo- 

 turus is a primitive one, but it seems more prob- 

 able that the organ has degenerated on account 

 of the presence of the choanal valve. 

 J. F. Daniel (University of California) : The 



EndosTceleton of Heterodontus francisci. 

 F. D. Barker (University of Nebraska) : The 



Parasites of the Muskrat. (Lantern slides and 



demonstration.) 



With the exception of a brief note by Leidy, 

 1888: 126, there is no reference to or description 

 of the parasites of our common muskrat. 



A recent examination of 27 muskrats trapped 

 along the Loup Eiver in Nebraska revealed a 

 heavy parasitic infection. Over 600 worms were 

 found, including trematodes, cestodes and nema- 

 todes. Seven species of trematodes, one species of 

 cestode and two species of nematodes vrere repre- 

 sented. 



The work on the trematodes which is now com- 

 pleted shows all seven species to be new and 

 heretofore undescribed with one possible excep- 

 tion, and in that case there is only the meager 

 description of Leidy referred to above. 



The large number of different and new species 

 of parasites which occur in the muskrat but 

 emphasizes the virgin and fertile nature of the 

 field of parasitology for the investigator and also 

 emphasizes the need and the value of a thorough 

 survey of the parasitic fauna of our common 

 animals by states, or better, by smaller units of 

 area. 



The description of one of the trematode para- 

 sites of the muskrat has been published and the 

 descriptions of the other six species will appear 

 soon. 



E. J. GiLMOEE (introduced by F. C. Waite) : 

 Variations in the Pelvic Girdle of Diemyctylus 

 mridescens. 

 W. E. Sullivan (introduced by F. C. Waite) : 

 Zones of Growth in the Skeletal Structures of 

 Fsexidopleuronectes americanus {Walh). 

 W. A. WiLLAED (University of Nebraska): (1) 

 The Epidermal Sense Organs of Anolis caro- 

 linensis. {2) A Case of Complete Twin Forma- 

 tion in Squalus acanthias. 



COMPAKATIVE PHYSIOLOGY 



Max Morse (Trinity College) : The Bole of 

 Phagocytosis in the Process of Involution. 

 Involuting organs, such as the tail of the anouri- 



dan larva, their gills, etc., have been described by 



Metchnikoff and others as atrophying through 

 phagocytosis. Metchnikoff believed that the 

 phagocytes arose from the muscle cells themselves, 

 but sections through organs at the time of degen- 

 eration show no mitoses in the muscle cells. 

 Others, such as Mercier, believe that the leuco- 

 cytes act as phagocytes and cause the breaking 

 down of the organs, but differential counts of 

 blood from young larvfe, those during metamor- 

 phosis and from adults show no correlations which 

 would indicate that polynuclear leucocytes, baso- 

 philes, eosinophiles, large or small mononuclear 

 leucocytes play any rSle in the process. The 

 process of atrophy here is similar in essential 

 respects to the involution of the uterus in mam- 

 mals, to the degeneration of the individuals of the 

 bryozoan colony, etc., where the process is doubt- 

 less autolysis and experiments are in progress, 

 which seem to show that this is the case in the 

 metamorphosing amphibian larva. 

 A. G. Mayer (Carnegie Institution) : Some Ef- 

 fects of Ions upon the Movements of Marino 

 Animals. 

 J. F. Abbott (Washington University) : Reac- 

 tions of Fiddler Crabs to Salt Solutions. 

 H. M. MacCuedy (Alma College) : Some Effects 



of Sunlight on the Starfish Asterias foriesii. 

 S. O. Mast (Johns Hopkins University) : The 

 Reactions of Spondylomorum to Light, with 

 Special Reference to the Question of Changes 

 in the Sense of Reactions. 

 H. W. Band (Harvard University) : Reactions of 

 the Tentacles of Sagartia lucice to Tactile 

 Stimulation. 



The reactions of tentacles of Sagartia. luciw to 

 tactile stimulation vary from a minimum reaction 

 consisting of a slight longitudinal contraction in 

 a narrow zone at the level of the point stimulated, 

 to a maximum contraction of the entire tentacle. 

 Occasionally the response extends to neighboring 

 tentacles or even involves the entire animal. In a 

 certain animal at a certain time the degree of the 

 response varies with the intensity of the stimulus. 

 But in the same animal at different times, or in 

 different animals at the same time and under 

 similar conditions of experimentation, the reac- 

 tions show great variation. 



Two distinctly opposed physiological conditions 

 were noted. In the one condition (designated as 

 positive) the distinctive feature of the reaction 

 is a bending of the tentacle at the point stimulated 

 and toward the stimulated side. In this condition 



