ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
385 
flattened dorso-ventrally, stretching backwards on the floor of the 
segment. Finally it widens slightly, and opens below the base of the 
parapodium. Nephridia occur in all the segments which have ciliated 
organs, and the lip of the nephrostome is directly continuous with the 
ventral prolongation of the ciliated organ. In Tyrrhena the condition of 
ciliated organs and nephridia is very much the same as in Hesione. 
In Nephthys the ciliated organ is somewhat like the shell of Peclen , 
smaller and more rounded than in Hesione, with no communication with 
the lumen of the nephridium. In both sexes there is a pair of ciliated 
organs in every segment except about the first ten. 
The nephridium of Nephthys is remarkable. It has no internal 
opening, but ends in a hunch of short blind branches, composed of 
unique “ tube-b6aring ” cells with flagella. There is an internal cur- 
rent towards the external pore, and it seems likely that excretion takes 
place through the walls. Possibly the thin-walled tubes in which the 
flagella work act as osmotic filters, while solid excretory products may 
be conveyed to the lumen of the canal by the cells themselves. The 
morphological interest of the facts will be discussed in a subsequent 
paper. 
Phagocytic Organs in Marine Annelids.* — Dr. J. Cantacuzene has 
made observations on Nephthys margaritacea, Glycera convoluta, Arenicola 
piscatorum , and Spirographis Spallanzanii , as regards their phagocytosis. 
His method was to inject carmine (in suspension in sea-water) into the 
body-cavity, and to investigate the points where the colour was tem- 
porarily localised. It may be noted at the outset that the carmine was 
never found free after 48 hours. 
The phagocyte apparatus is represented by (1) the amcebocytes ; 
(2) the endothelial cells of the coelome and their fixed derivatives, the 
lymphoid glands or masses ; and (3) the nephridial cells. The endo- 
thelial cells which act as phagocytes lose their flat shape, and project 
singly or in groups into the general cavity, especially in the parapodia. 
The lymphoid masses result from the proliferation of endothelial cells, 
and occur both irregularly and quite symmetrically. In the nephridial 
cells the carmine was always localised between the nucleus and the free 
margin of the cell. In all cases the solid particles are enclosed in a 
vacuole or lacuna, the contents of which become rose-coloured as the 
carmine passes into liquid form. 
Structure and Development of Spirorbis borealis.f — Mary A. 
Schwely has studied this Chsetopod. There are 14-20 segments; the 
prostomium bears eight branchiae (including the operculum ; prostomium 
and peristomium coalesce in a buccal somite; thoracic and abdominal 
regions are distinguishable ; the parapodia are very slightly developed ; 
the alimentary system consists of a short fore-gut, a short hind-gut, and 
a long mid-gut ; the gut is surrounded by a blood-sinus ; the shell-gland 
lies in the anterior thoracic region, in the median ventral line. The 
body undergoes considerable modification during development, being 
greatly influenced by the shell. The animal is hermaphrodite, and has 
* Comptes Rendus, exxv. (1897) pp. 326-8. 
t Proc. Acad. Sci. Philad, 1897, pp. 153-60 (2 pis.). 
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