170 H. M. FUCHS. 



Fig. 10. — Larva of Olyccra. 10 days. 

 Side view. ap. c. — Apical cilia, m. — Mouth. 



As has been pointed out by Shearer (7), the typical Trochophore is 

 confined to a very limited number of Annelids, occurring, in fact, only 

 in Serpulids and Polygordhis. The larvae of the remaining forms, 

 which have a pelagic stage, mostly resemble the two described above. 

 They differ from the true Trochophore in form, opacity, shape of the 

 gut, in the absence of a head-kidney and in the small amount of 

 blastocoele. The early Neijhthys larva figured by Claparede and 

 Mecznikow (2), however, seems to approach closely to the form of a 

 true Trochophore. They state that a whole series of intermediate 

 forms were collected from the Plankton, up to the stage when the 

 bristles were recognizable, so that there could be no doubt of the 

 identity of the larva. Later observers, however, have described quite 

 another type of larva for Nephthys, and one closely approaching 

 that of N. Hombergi. 



REFERENCES. 



1. Allen, E. J., and Nelson, E. W. " On the Artificial Culture of Marine Plankton 



Organisms." Journ. Marine Biol. Assoc, vol. vii, p. 421. 1910. 



2. Claparede, E., and Mecznikow, E. " Beitrage zur Kentniss der Entwickelungs- 



geschichte der Chaetopoden." Leipzig, 1868. 



3. Fewkes, J. W. "On the Development of Certain Worm Larvre." Studies 



from the Newport Marine Zool. Lab. Bull. Mus. Comp. Zool. Harv. Coll., 

 vol. II. 1883-5. 



4. Gravely, F. H. L.M.B.C. Memoirs, xix. " Polychaete Larvte." 1909. 



5. Hacker, V, " Pelagische Polychaetenlarven." Zeit. fur Wiss. Zool., 1897, p. 74. 



6. Lillie, R. S. "The Structure and Development of the Nephridia of Arenicola 



cristata." Mittheil. a.d. zool. Sta. zu. Neapel, 17 Bd., 3 Heft, 1905. 



7. Shearer, C. "On the Development and Structure of the Trochophore of 



Hydroides undnatus." Q. J. Micr. Sci., vol. LVI, p. 543. 1911. 



8. Treadwell, A. " The Cytogeny of Podarke obscura." Journ. Morph., vol. xvii, 



p. 399. 1901. 



9. Wilson, E. B. "The Cell-lineage of Nereis." Journ. Morph., vol. vi, p. 361. 



1892. 



