16 PROCEEDINGS OF THE NATIONAL MUSEUM vol.80 



average of 3,357. In October, the total of 28 stations was 116,000, 

 an average of 4,143. In December, 27 stations yielded a total of 

 129,350 specimens, an average of 4,791. 



There were thus four rises and four falls during the year, corre- 

 sponding to the four breeding periods, but the rise in March and 

 that in the following fall were much greater than the others. The 

 lowest minimum was found in June and was probably the result of 

 the increased abundance of young fishes and other animals that prey 

 upon the copepods. 



No development stages were found at any of the stations near the 

 inner end of the bay, but no positive statement can be made with 

 reference to the ability of any of the copepods to breed in water of 

 low salinity. The records do indicate, however, that water of higher 

 salinity is more favorable for breeding purposes, since development 

 stages practically disappeared at the mouth of the Potomac River, 

 and were not found in any numbers above there except at Station T. 



TRIP TO 100-FATHOM LINE 



Supplementing the survey of the bay, a trip was made to the 

 100-fathom line on August 21, 1920, to ascertain which of the species 

 found in the bay were also present in the outside ocean and what 

 species, common in the outside ocean, did not enter the bay.^ Hauls 

 were made with surface and bottom nets at depths of 118, 67, 40, and 

 20 fathoms, and on the following day at a depth of 10 fathoms. 



Forty-one species were collected during this trip, an exceptionally 

 large number, but all of them except one or two were obtained in 

 sufficient numbers to show that they were at least common. Nine- 

 teen species, designated in Table 3 by footnote 2, were not found 

 inside the bay. The other 22 species were found both in the bay 

 and in the ocean, and included every one of the 10 species that were 

 universally distributed throughout the bay. 



In contrast with this, 23 species, including all the new forms, 

 were present in the bay but were were not found in the ocean. These 

 are designated by footnote 3 in Table 1, giving the seasonal dis- 

 tribution of the species. 



The species found in greatest numbers in the ocean proved to be 

 Centropages typicus. Next to this came Paracalarms parvus and 

 then in order Calanus ■jinmajrchicus^ Metridia lucens, Candacia 



2 In lien of the original chart of the stations outside of Chesapeake Bay, which seems no 

 longer to be extant, Dr. R. P. Cowlos, in charge of the survey, has furnished the following 

 Information regarding their position : 



" Our log shows that Station 8832 was on the 100-fathom curve whore a line, run E. 

 5/8 S. from the whistle buoy 'FIR' off Cape Henry, cuts in. Stations 8833, 8834, 8835, 

 and 8836 were on the 60, 40, 20, and 10 fathom curves, respectively, where the same line 

 menlloned cuts them. I feel quite certain that the line follows the compass course." 



