CTENOPHORES IX NEW JERSEY COASTAL WATERS. 1 05 



or heavier." Unfortunately for the purposes of this discussion 

 there are no data as to the relative abundance of Mnemiopsis or 

 of other plankton feeders in the several region-. 



The relative reduction in numbers of oyster larva- in 1921 and 

 in 1923 is of interest. For example, on June 25, 1921, the 

 average number of earliest straight hinge oyster larva; per 100 

 liter- i.f \\aier, collected at 7 stations on Barnegat Hay. was 

 joo. On the 2;th, by which time the larva? were entering on 

 t!n- e.irly iimbo stage, the average number of these larva- \\as 

 found to have been reduced to 8,700, representing a quite usual 

 precentage of mortality. In 1923, on June 23, at the central 

 rolle. tin- station near the middle of the bay where the early 



ster larvae have been first found in abundance for three siic- 

 sive years, there was obtained a total of 60,850 larva- per i<>. 

 lit rrs. Tuo days later the average of 8 stations -ln>\\r.l Inn 54 

 of these larvae remaining per 100 liters, the largest single catch at 

 any one station being 200. So far as known there wen present 

 diirini; 1923 no other factors aside from vast swarms of Mncmi- 

 <>/><is which were not also operating in 1921. 



It is worth while to add a comparison between oyster sets 

 found in Harnegat Hay by late August, 1923, with those at otlu-r 

 03 ster producing areas of New Jersey. In the Mullica River an 

 Unit set of oysters one week old was found on August 30. 

 At thi-> date only an occasional Mnemiopsis was seen. Although 

 no ol.-erx ations were made in this area earlier in the season there 

 i- no reason for believing that the ctenophores were more abun- 

 dant during the preceding 3 weeks, during which time the oyster 

 lar\ a \\onld have matured and set, than they were on the date of 

 m\ O|>M i \ations. In Delaware Bay also the usual oyster set 

 M -,-urred. The waters of this area are so stormy and turbid near 

 tin- shore that Mnemiopsis cannot thrive there, although the 

 much hardier Beroc appears there in abundance in September, as 

 already stated. 



VI. 



DISCUSSION OF SPECIES. 



To the student of the Ctenophora it is apparent that certain 

 \\ide discrepancies occur between the account of the distribution 

 of the three i i enophores discussed in this paper and 



