Mat 27, 1910] 



SCIENCE 



837 



Somniosus microoephalus Le Seur is common 

 in Icy Straits. Its range extends through the 

 Arctic waters to the North Atlantic. Specimens 

 examined in Europe are regularly infested with a 

 gill parasite, Squaloncliocotyle borealis. This 

 eetoparasitic trematode undergoes, no doubt, 

 direct development. It occurs abundantly on 

 Aiaskan specimens of the same host. Four other 

 internal parasites are recorded from this host in 

 the Atlantic. These undergo probably indirect 

 development and hence need one or more inter- 

 mediate hosts. The sleeper shark in Alaska har- 

 bors species from the same genera as those in the 

 Atlantic, but they are related rather than iden- 

 tical parasites. As in the case of land animals, 

 so in this marine host, the species of parasites 

 which infest it vary in different portions of its 

 range. 



Some New Cases of Trihedral Tcenia: F. D. 



B.iBKER, University of Nebraska. 



The examination of 37 dogs at the University 

 of Nebraska from November, 1903, to April, I9I0, 

 yielded 601 Tcenia serrata and 450 Tcenia serialis 

 in addition to a large number of other species of 

 Tceiiice. Among the T. serrata were four trihedral 

 or prismatic taeniae and among the T. serialis 

 were three trihedral forms. This increases the 

 number of reported trihedral taenia to thirty 

 cases and adds two new species to the list. The 

 specimens resemble two tapeworms, the one fused 

 along its side to the face of the other. Each 

 scolex has six svickers arranged in three groups 

 of two each. The rostella are armed with two 

 rows of hooks, but the number of hooks in each 

 row is less than the normal. One or two genital 

 pores occur in each mature proglottid, one pore 

 to a crest. The trihedral condition affects the 

 musculature, the nerve trunks, the excretory 

 canals and the reproductive organs. The oncho- 

 spheres have six to twelve hooks. 



These trihedral forms probably arise from a 

 double embryo produced by the partial separation 

 ol the first two or early blastomeres and not by 

 a fusion of two normal embryos. 



A Comparative Study of the Development of the 



Sympathetic Nervous System in Birds and 



Mammals: Albebt Kuktz, University of Iowa. 



Medullary cells migrate from the neural tube 



into the ventral nerve-roots. With similar cells 



which wander out from the spinal ganglia, these 



cells migrate peripherally along the spinal nerves. 



Some of these cells deviate from the course of the 



spinal nerves and give rise to the sympathetic 



trunks and the prevertebral plexuses. The vagal 

 sympathetic plexuses, viz., the cardiac plexus and 

 the sympathetic plexuses in the walls of the 

 visceral organs, arise from cells which migrate 

 from the hind-brain and the vagus ganglia along 

 the vagi. 



The great majority of the cells which migrate 

 peripherally from the neural tube and the cerebro- 

 spinal ganglia are the " indifferent " cells of 

 Sehaper. Among these are found a few " neuro- 

 blasts " of Sehaper. Therefore, the sympathetic 

 neurones are homologous with the efferent and 

 the afferent components of the other functional 

 divisions of the peripheral nervous system. 

 Mitotic figures occur occasionally along the course 

 of migration and in the sympathetic anlagen. 

 We are not to suppose, therefore, that all the cells 

 taking part in the development of the sympa- 

 thetic system actually migrate as such from their 

 sources in the cerebrospinal system. Doubtless, a 

 goodly number arises by the mitotic division of 

 '■ indifferent " cells along the course of migration. 



Certain morphogenetic differences occur in the 

 development of the sympathetic system in birds 

 and mammals which, doubtless, indicate that the 

 sympathetic system has departed more widely 

 from the original type in birds than in mammals. 



The sympathetic system may be looked upon as 

 an accession to the nervous system which has 

 arisen comparatively late in the evolution of verte- 

 brates in response to the conditions of the vege- 

 tative life. 



The Histology of the Nasal Mucous Membrane in 

 Mammals: Wm. A. LoCT, Northwestern Uni- 

 versity. 



An illustrated account of the structure and of 

 the histogenesis of the nervous elements in the 

 sensory epithelium of the nose of the pig and 

 rabbit with some remarks on the question of the 

 direction of growth of nerve fiber. 

 The Lymphatic System of Turtles: Feank A. 

 Stbomsten, University of Iowa. 

 The points considered in this paper ■\\ei-e the 

 anatomy of the lymphatic system of Ghrysemys 

 marginata and the development of the lymph 

 hearts of the loggerhead turtle. A preliminary 

 paper with figures giving the results of this in- 

 vestigation is to be published at once elsewhere. 



The Bermuda Biological Station for Research: 

 P. W. Carpbntee, University of Illinois. 



The Work of the Illinois Biological Station: 

 Stephen A. Foebes, director, Illinois State 

 Laboratory of Natural History. 



