ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 1593 



its bifid brancliia3. Gaps in previous descriptions of a number of 

 Aphroditidffi are now filled up. The collection confirms the author's 

 view that Polychfetes cannot be satisfactorily referred to zooloojii^al 

 provinces. Temperature is the main factor in determining thiir 

 distribution. 



Nematohelminthes. 



Notes on Nematodes.* — N. A. Cobb continues his contributions to 

 " a science of nematology." He finds hints of segmentation in the 

 disposition of the seta3. Some of the cephalic setaj are jointed, and 

 are compared to segmented appendages. This is illustrated in reference 

 to Fomponema miraUle g. et sp. n., ScaptreUa cincta g. et sp. n., and 

 Chironchus vorax g. et sp. n., three remarkable free-living marine types. 

 In a species ot Selachinema the "dorsal jaw" is vestigial, so that the 

 two projecting " mandibles " become practically lateral, and the tri- 

 lateral symmetry of the Nematode head is changed to bilateral. 



On the beach-sand between tide-marks at Wood's Hole it was cal- 

 culated that in one area there were on the top three inches of sand 

 at least 527 millions of Nematodes per acre. On another beach there 

 were at least 1040 millions per acre in the topmost inch of sand. On 

 muddy shores the Nematode population is much more dense— thousands 

 of millions per acre. 



A new " locational " nomenclature is suggested for the varied relations 

 of sexual reproduction and of the intracellular elements. Thus we 

 have syngonic, digonic, amphigouic, homogonic, etc. ; syncystic, 

 dicystic, amphicystic, homocystic, etc. 



New Ascarid of the Frog.f — L. G. Seurat describes Porrocaecum 

 numidicum sp. n. from the duodenum of Rana ridibunda. In the shape 

 of its buccal lips, in the disposition of the caudal ala3 and of the 

 genital papilla of the male, it is near Orneoascaris chrysanthemoides 

 Skrjabin, from the intestine of an East African species of Biifo, but it 

 has much smaller spinules and a dorsal intestinal cfficum. It is quite 

 distinct from Ascaris brevicauda of the newt. 



New Acanthocephala from Birds. | — H. J. Van Cleave has found 

 in the Collections of the U.S. Bureau of Animal Industry four new 

 Acanthocephala from birds— one belonging to the genus Genirorhynchus 

 and three with characters which exclude them from any knowii genus, 

 and warrant a new genus, Mediorhynchus. The two genera agree in the 

 way in which the proboscis receptacle finds the insertion near the middle 

 of the proboscis wall, and in their occurrence within the alimentary 

 canal of birds. They differ in the size, shape, and number of the cement 

 glands of the male ; in the structure of the wall of the proboscis 



* Notes on Nematodes. Baltimore: Waverly Press, 1917, pp. 117-28 (7 figs.). 



t O.K. Soc. Biol. Paris, Ixxx. (1917) pp. 94-7 (2 figs.). 



X Trans. Amer. Micr. Soc, xxxv. (1916) pp. 221-32 (.3 pis.). 



Aiig. mil, 1917 2 D 



