150 E. W. MACBRTDE. 



to the stone canal suggests a comparison of the origin of the 

 genital cells near the uephridia in many Annelids, but the 

 homology of the stone canal with a nephridium has yet to be 

 proved. 



In conclusion I have to express my warmest thanks to 

 Dr. H. Eisig and Dr. ?P. Mayer for many valuable sugges- 

 tions, especially to the latter for his invaluable assistance 

 with technique. 



List of Works referred to in this Paper. 



1. Apostolides, Nicolas Christo-. — " Anatomic et Ueveloppement des 



Ophiurides," ' Arcliives de Zoologie Expdrimentale,' x, 1882. 



2. Bury, H. — " Early Stages in tlie Development of Antedon Rosacea," 



' Phil. Trans. Royal Soc.,' London, vol. clxxix. 



3. Bury, H. — " Studies in the Embryology of the Echinoderms," ' Quarterly 



Journal of Microscopical Science,' April, 1889. 



4. CuENOT, L. — " ^^tudes auatomiques et morphologiques sur les Ophiures," 



'Archives de Zoologie Experim,entale,' tome vi, 1888. 



5. CuENOT, L. — "Contribution a, I'l^ltude anatomique des Asterides," 



' Archives de Zoologie Experiraentale,' tome v bis, supplementale. 



6. CuENOT, L. — " liltudes morphologiques sur les l^chinoderms," 'Archives 



de Biologie,' tome xi, fascicles 1 and 2. 



7. Hamann, Otto von.— " Anatomie der Ophiuriden und Crinoiden," 



' Jenaischen Zeitschrift Nat. Wiss.,' Bd. xxiii. 



8. Hamann, Otto von. — "Die Wandernden Urkeimzellen und ihre 



Reifungs - static bei den Echiuodermen," 'Zeitschrift fiir wiss. 

 Zoologie,' 6 d., 46, 1880. 



9. Kohler. — "Recherches sur Tappareil circulatoirc des Ophiures," 



'Annales des Sciences naturelles— Zoologie,' 1887, H. 7. 



10. LuDWiG, H. — " Beitrage zur Auatoniie der Ophiuriden," ' Zeitschrift fiir 



wiss. Zoologie,' Bd. xxxi, 1878. 



11. LuDWiG, H.— " Neue Beitrage zur Anatomic der Ophiuriden," ' Zeit- 



schrift fiir wiss. Zoologie,' Bd. xxxiv, 1880. 



12. LuDWiG, H. — "Entwickelungsgeschichte von Astcrinagibbosa,"'Zeit- 



schrift fiir wiss. Zoologie,' Bd. xxxvii, 1882. 



