456 SUMMARY OF CDRUENT RESKARCHES RELATING TO 



branches which cuuuect the testcK with the vasa deforentia are 

 developed from the mesodermal coating of the testes. 



Muscles of Chaetopoda.* — Dr. E. Rohde finds that amongst the 

 Oligochfota, the Limicola^ have the simi)lest musculature, the longi- 

 tudinal layer consisting of (unstriped) fibres running parallel to each 

 other. Each fibre has a contractile fibrillar periphery and a central 

 cavity. In Terricolse, on the other hand, the — otherwise similar — 

 fibres are usually united to form bundles with a contractile perijihory 

 and au axial cavity. The feather-like arrangement of fibres of wliich 

 Claparede speaks, was not seen by Kohde in all species of Ltimbricus. 

 No bundles occur in the circular muscles. 



As regards Polychaeta, Serpula and ProUda have bundles of 

 longitudinal muscle-fibres, as in the typical Terricolte. In Spirographis 

 the bundle arrangement is only partial, and in all other Polychteta 

 investigated could not be traced at all. In this group the structure of 

 the fibres is as in Oligocheeta, and they lie imbedded in a similar 

 multinucleate fibrillar connective tissue. 



Elytra of some Pclynoina.f — According to Dr. E. Jourdan, these, 

 like Aphrodite, show a cuticle bounding their two surfaces, and a 

 hypoderm beueath either surface connected by fibrillao. Chitinous 

 disks may be seen in process of formation in the cuticular layer. The 

 irregularities of surface are either "warts" which are large, prickly, 

 and without function, or sensory " papillae" which are small and 

 circular in optical section, consisting of a chitinous cuj) (shaped like 

 a wine-glass without a stem) covered by a saucer-like cuticular cap, 

 and Containing granular non-nucleate protoi^lasm into which pene- 

 trates a nerve-fibril from the fibrillar layer. Nerve-cells were found 

 beneath the hypoderm surrounding the fibril, and constituting a small 

 racemose ganglion. 



Pohjnoe torquata is phosphorescent, and this phenomenon is not 

 due, accordiiig to Jourdan, to the numerous nervous fibrils traversing 

 the elytra, as Pauceri maintained. Phosphorescence here occurs in 

 definite regions, and is due to cells of the hypodermis (Jourdan calls 

 it epidermis) of the inferior surface of the elytra, which is locally 

 transformed into phosphorescent mucous cells. As regards the internal 

 tibrillfe, they would appear to be identical with what Claparede 

 variously calls fibrillar hypoderm and stellate connective tissue. 



New Arenicola from Arctic Alaska.; — Mr. J. Murdoch describes 

 Arenicola glacialis n. sp. from Arctic Alaska. It is closely allied to 

 A. marina, but has ouly six setigerous segments anterior to the gills, 

 and eleven gill-bearing segments instead of seven and thirteen. 



Histriobdella homari.§ — M. A. Foettinger renames this worm, 

 which does not ap2)ear to be a leech, Histriodrilus benedeni. After a short 

 sketch of what has been hitherto known of this form and an account 

 of its external characters, the various organs are dealt with in detail. 



* Zool. Anzeig., viii. (1885) pp. 135-8. 



t Ibid., pp. 128-34. 



J Trur. U.S. Nat. Mus., vii. (1885) p. 522. 



§ Arcli. do Biol., v. (1884) pp. 434-516 [H pie.). 



