2 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 123 



The station data for the collections of ostracods used in this study 

 are as follows : 



We are grateful to Dr. Roland L. Wigley, Bureau of Commercial 

 Fisheries Biological Laboratory, Woods Hole, Mass., for ostracods 

 from Great Harbor and Lake Tashmoo; to Mr. J. Stewart Nagle, 

 Marine Biological Laboratory, Woods Hole, for ostracods from Hadlejr 

 Harbor, and to Mrs. C. R. Stoertz, Department of Paleobiology, 

 Smithsonian Institution, for ostracods from stations 1, 6, and 7 

 from Martha's Vineyard. We thank Mrs. Carolyn Bartlett Gast for 

 final preparation of the ostracod figures from camera lucida drawings 

 by Kornicker. 



Life history of Sphaeronellopsis monothrix. — From the specimens 

 in our collections (p. 3) it is possible to reconstruct some details of 

 the life history. It is obvious from the account that follows that our 

 knowledge of many phases of the life history is either fragmentary or 

 completely lacking. We hope that the ready availability of the 

 species at Woods Hole and perhaps elsewhere on the Atlantic Coast 

 will lead others to investigate more intensively the biology of this 

 interesting parasite. 



The motile stage by which Sphaeronellopsis spreads from one 

 ostracod to another is the copepodid, which swims by means of the 2 

 pairs of flat, setose trunk legs. Copepodids found in an ostracod 

 marsupium without accompanying adult copepods or ovisacs are 

 interpreted as recently having invaded the hosts. Since they do not 

 differ in size or morphology from copepodids still within the ovisac 

 membrane, there appears to be only one copepodid instar. The 

 copepodid normally does not enter immature ostracods; we have not 

 found any infestation in female ostracods less than 1.30 mm long. 



Spermatophores were attached to 2 female copepods, .23 and .36 

 mm in length, indicating that mating may take place when the female 

 is very young or may be delayed until she is older. Only 3 male 



