31 



No. 3. Contributions from the Zoological Laboratory. — XXVI. On some 

 Points in the Morphology and Histology of Sipunculus nudus, L. By 

 H. B. Ward. pp. 42. 3 Plates. May, 1891. 



No. 4. Three Letters from Alexander Agassiz to the Hon. Marshall 

 McDonald, on the Dredging Operations off the West Coast of Central 

 America to the Galapagos, to the West Coast of Mexico, and in the Gulf of 

 California, carried on by the U. S. Fish Commission Steamer "Albatross." 

 pp. 16. June, 1891. 



No. 5. Contributions from the Zoological Laboratory. — XXVII. The De- 

 velopment of the Pronephros and Segmental Duct in Amphibia. By 

 H. H. Field, pp. 140. 8 Plates. June [August], 1891. 



