STRUCTURE OF THE EXCRETORY ORGANS OP AMI'HIOXUS. 201 
limit of the series of nephridia. Presumably the dorsal 
solenocytes degenerate later^ since they are not known to 
exist in the adult. 
The observations on the larval nephridia recorded in this 
part may be summarised as follows : — To every gill-slit 
corresponds a uephridinng consisting of a sac closed in- 
ternally, but opening to the exterior apparently at the point 
where the ectoderm joins the endoderm in the shallow bran- 
chial chamber. From the internal blind end of ihe nephridial 
sac spring numerous solenocytes, some of which reach and 
spread over the aorta at every segment in a fan-like arrange- 
ment. This structure is only fully developed from about the 
eighth segment backwards to the last nephridium. 
July 3rd, 1909. 
List of Kffkkfncks. 
1. Hoveri, Tli. — “Die Niereiikauiilcheii des Aiiiphioxiis," ’Zool. Jahrl). 
Aiiat. Abt.,’ Bd. 5, 1892. 
la. “ Bemerk. iiber d. Ban. d. Niereiikaiialcheii des Ampliioxus," 
‘ Aiiat. Aiiz.,’ Bd. 25 , 1904. 
2. Felix, W. — “Entw. des Hainapparates," ‘ Hertwig’s Handbucdi d. 
Eiitw. d. Wirl^eltiere,’ Bd. 3, 1904. 
3 . “ Entw. des Exkretions-system,” ‘Aiiat. Hefte. Ergeb. Aiiat. 
11 . Entw.,’ Bd. 13, 1904. 
4 . Goldschmidt, R.— “Ampliiuxides,” ‘ Wiss. Ergel). d. deutscli. Tiefsee- 
Expedition “Valdivia,”’ Bd. 12, 1905. 
5. Goodrich, E. S.— “On the Cadom, etc,” ‘Quart. Journ. Micr. Sci.,’ 
vol. 37, 1894. 
6 “ On the Nephridia of the Polycha-ta,” Parts I, II, and III, 
ibid., vols. 40, 1897, 41, 1898, and 43, 1900. 
7. “ On the Structure of the Excretory Organs of Ainphioxus,” 
Part I, ibid., vol. 45, 1902. 
8. “ On the Body-cavities and Nephridia of the Actinotrocha 
larva,” ibid., vol. 47, 1903. 
9. Hatschek, B. — “ Mitth. iiber Ainphioxus,” ‘ Zool. Anz.,’ Bd. 7, 1884. 
