ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 203 



appendages are visible behind the three original pairs. A little later 

 the body becomes elongated, and divided into two distinct regions — the 

 rudiments of future carapace and abdomen. The anterior region shows 

 traces of segmentation. This stage may be described as the meta- 

 nauplius, and after a moult becomes converted into a protozonoa. 



Annulata. 



Nephridium of Nephthys caeca.* — Mr. F. H. Stewart has confirmed 

 Mr. E. Goodrich's results in all points except one, the position of the 

 organ relative to the blood-vessels. 



He describes the process of excretion in the following terms : — 

 ^Yhenever a particle of solid excretory matter appears in the coelom it is 

 immediately engulfed by one of the phagocytes. This, when it has 

 become sufficiently loaded, passes into the neighbourhood of the ciliated 

 organs, either by its own amoeboid motion or by the agency of the 

 currents raised by the cilia. Here it is swept down one of the grooves, 

 and joins the little mass of its fellows raised against the barrier of the 

 nephridial tube. Partial degeneration now sets in, and the phagocyte 

 appears to enter bodily the protoplasmic wall of the canal, carrying the 

 foreign matter with it. The latter then passes out either by the lumen 

 of the canal, assisted by the cilia, or by passing along through the wall 

 itself. The whole nephridium is constantly moving, the ciliated organ 

 swaying up and down, tbe tube also moving upward and downward on 

 the blood-vessels to a limited extent. These movements no doubt facili- 

 tate ingestion of refuse. 



British Species of Siphonostoma.t — Miss M. T. Newbigin notes that 

 the two most familiar species of Siphonostoma (Flabelligera) are S. affinis, 

 the typical northern form, and S. diplochaitos, the typical Mediterranean 

 form. Specimens collected at Millport agreed most closely with S. diplo- 

 chaitos Otto, specimens from Plymouth with S. affinis Sars, as defined by 

 St. Joseph. But 8. diplochaitos changes in character during growth, the 

 changes occurring in those special characters which serve to differen- 

 tiate the adult from S. affinis ; the young of the former approximates to 

 the adult of the latter. In fact it seems probable that S. diplochaitos 

 is a very variable species, exhibiting a strong tendency to run into 

 local races, and that the three " species," S. diplochaitos, S. affinis, and 

 S. claparedii, are only varieties of one species. 



Epidermal Organs of Phascolosoma.iJ: — Miss Margaret Nickerson 

 publishes a brief note on certain remarkable intracellular canals in the 

 skin of P. goulcli. Certain of the epidermal organs consist of ovoid sacs 

 surrounded by a membrane, and containing twenty to thirty very large 

 gland-cells. In each of these gland-cells there is an intracellular am- 

 pulla which lies above the nucleus and'communicates with a canal. The 

 canals from the different cells unite together to form a main duct which 

 opens to the exterior by a pore at the summit of the organ. The exact 

 appearance presented is not constant, but varies with the different con- 

 ditions of functional activity of the organ. Somewhat analogous struc- 

 tures occur in certain of the glands of Insects and Crustacea. A full 

 account of all the epidermal organs of Phascolosoma is promised. 



* Ann. Nat. Hist., v. (1900) pp. 161-4 (2 pis.). t Tom. cit., pp. 190-5 (1 pi.). 

 X Zool. Jahrb. (Abth. Anat.), xiii. (1899) pp. 191-*J (1 pi.). 



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