. Fresh-water biology. Freshwater biology. FREE-LIVING NEMATODES 495 46 (45) Pharynx not long and narrow 47 47 (48) Striae not resolvable into rows of dots Cephalobus Bastian. Genus of numerous species, frequent about the higher plants, doubtless often at least "semi- ;_ Occasionally species in fresh water. Common in decaying vegetable matter. Some species are parthenogenetic, others hermaphroditic. Found on the surface of insects. Cephalobus resembles Rhabdilis, but may readily be distinguished by the form of the pharynx and the nature of the male caudal armature. The phar
. Fresh-water biology. Freshwater biology. FREE-LIVING NEMATODES 495 46 (45) Pharynx not long and narrow 47 47 (48) Striae not resolvable into rows of dots Cephalobus Bastian. Genus of numerous species, frequent about the higher plants, doubtless often at least "semi- ;_ Occasionally species in fresh water. Common in decaying vegetable matter. Some species are parthenogenetic, others hermaphroditic. Found on the surface of insects. Cephalobus resembles Rhabdilis, but may readily be distinguished by the form of the pharynx and the nature of the male caudal armature. The pharynx of Cephalobus is almost never cylindroid or prismoid as in Rhabdilis. On the contrary it tends to taper more or less regularly from the base of the lips backward. Though simple in form the pharynx is usually compounded of two or three series of short cuticula elements separated from each other by transverse breaks. In a considerable number of species the lips are modified so as to bear more or less complicated forward pointing cuticula appendages. Such forms are intermediate between the typical Cephalobi and other genera, such as Acrobeles and WUsonema. The males of the Cephalobi do not possess a bursa, at most showing faint indications of such a structure. Nevertheless the papillae or ribs found accompanying the bursa in Rhabdilis are present in Cephalobus, though they sometimes are less numer- ous than on typical Rhabdites. Not infrequently the ovary functions in the first instance as a testis. Spermatocytes appear in the young ovary even before an external sexual opening exists. The developing spermatozoa descend the oviduct and enter the uterus. Later the oocytes de- velop and are fertilized by the spermatozoa previ- ously produced in the same organ, — at least this happens in some instances, and hence is assumed to happen in all. So far no differences have been dis- covered between spermatozoa produced in this way by these syngonadic females and those produced by the
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectfreshwa, bookyear1918
