INITIAL STRATIGRAPHIC SURVEY OF NEMAS 



In the upper 20 mm. of 



MARINE BEACH SAND, NEAR LOW TIDE MARK 



CONTRIBUTIONS TO A SCIENCE OP NEMATOLOQY XXI 

 BY N. A. COBB 



In 1916 studies at the laboratory of the Bureau of Fisheries, Woods 

 Hole, Massachusetts, showed that sandy beaches, far from being 

 utterly barren, carry a comparatively rich fauna of microscopic organ- 

 isms. What biological and economic role these organisms may play is 

 little known. Conceivably they may be more important than would 

 at first be suspected. Recall that many larger aquatic organisms, 

 at one period or another, may pass a certain amount of time on the 

 bottom. During this sojourn their relationship to the microscopic 

 inhabitants of the sand, mud, etc. constituting the bottom, is a matter 

 about which we know very little, but it is easy to imagine that some- 

 times the relationship may be important. Again, the sand- and mud- 

 inhabiting organisms themselves may be temporary stages (eggs, 

 larvae) in a varied life history. 



Such thoughts led to a stratigraphic examination of marine beach 

 sand at Woods Hole, August, 1928. A small sheet-metal box, 10 

 centimeters square, carrying a series of thin metal slides was devised, 

 such that by its aid layers of sand 5 mm. thick, lying one above another 

 in series, could be collected (Figs. 1 and 2). In each of two collec- 

 tions four such successive horizontal layers were examined for their 

 nemas. The results are indicated in the following tables : 



Collection I: Layer No. I topmost 1st 5mm. 100 sq. cm. 905 nemas 



" II 2nd " " " 1,355 " 



" HI 3rd " " " 1,009 " 



" IV 4th " 175 " 



Collection II: Layer No. I topmost 1st 5 mm. 100 sq. cm. 1,512 nemas 



" II 2nd " 1,403 " 



HI 3rd " " " 981 " 



IV 4th " 226 " 



Only two collections were made, as the census is a very tedious one. 

 It will be seen that the two collections, taken a few yards apart, give 



Reprinted from the JOURNAL OF THE WASHINGTON ACADEMY OF SCIENCES, Vol. 19, 

 No. 10, May 19, 1929. 



