ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 983 



anterior segments the course of the circular and longitudinal vessels of 

 the midgut is so regular that the quadrate interspaces are always very 

 striking ; further hack the circular vessels branch somewhat irregularly, 

 and in the hindermost segments there is the most irregular communi- 

 cation of the several capillaries. It seemed to be impossible to regard 

 this vascular system as a mere blood-sinus, as Voigt has lately 

 suggested in the case of Branchiobdella. 



The dermal sensory organs of Ophidonais serpentina and Slavina 

 appendiculata are next mentioned ; in contradistinction to Mr. E. C. 

 Boi afield, the author finds that they are quite different in these two 

 genera. The generative organs of Nais elinguis are ripe in the second 

 half of February, at which time N. barbata is still reproducing itself 

 asexually by gemmation and fission ; the species, therefore, are 

 distinct, and ought not to have been united by Semper and Timm. 

 With regard to the details of their structure Herr Stole finds himself 

 in agreement with Vejdovsky. 



Histology of the Nervous System of Chsetopoda. * — Dr. E. 



Rohde gives an account of his investigations into the histology of the 

 nervous system of the Aphrodites. If Sthenelais be selected for the 

 study of the colossal nerve-fibres these are found to traverse the 

 whole nervous system from front to back, to run from behind forwards, 

 and starting in each segment on eacdi side from the nervous system, to 

 run to the periphery. They are the processes of colossal ganglion- cells. 

 The ganglion-cells are without exception unipolar, but in other points 

 of structure they exhibit great variation ; some are faintly granulated 

 and rather small, lie in large packets and have a pyriform shape ; 

 others are very large, spherical, and darkly granulated, and are 

 always arranged singly. Both kinds are devoid of a cell-membrane 

 and are imbedded in a network of fibres which appears to arise from 

 subcuticular cells. The colossal cells are traversed in all directions 

 by fibrils of different strengths, which issue from all points of the 

 periphery of the cell ; it is not certain whether the ganglion-cells are 

 united with one another by the fibrils. 



Antennae of Eunicidae.f — M. E. Jourdan finds that the antennre 

 of the Eunicidae consist of a cuticular envelope, an axial nerve, 

 and intermediate cells. The cuticle is exceedingly delicate, has no 

 glandular pore, but some very fine hyaline cilia. Below it there are 

 cylindrical cells, set in a single layer, which call to mind the arrange- 

 ment and form of the epend> ma of some vertebrates ; some of the 

 cells are rodlike, and there are also very fine fibrils arranged in 

 bundles among the epithelial cells ; the function of these last is 

 probably sensory. The cells have basal prolongations which inter- 

 lace and form a kind of fibrillar sheath around the axial nerve. 

 Some of the cells are bipolar, and there is every reason to suppose 

 that they are nervous in function. It would seem that the rods and 

 fibrillar bundles of the epithelial layer are especially sensory, and 

 that the other elements are protective and supporting. 



* SB. Preuss. Akad. Wiss., 1886. pp. 781-6. See Ann. and Mag. Nat. 

 Hist., xviii. (1886) pp. 311-6. f Comptea Rendus, ciii. (1886) pp. 216-8. 



