CThN'.PIIORES IX XEW JERSEY COASTAL WATERS. IOQ 



Plenrobrachia is undoubtedly adjusted to temperatures equal to 

 if not above those found during the summer in Barnegat Bay. 



Plenrobrachia brunnea may be a species or subspecies which is 

 deli< -ately adjured to a narrow range of temperature, since it is 

 found in the inland waterways of New Jersey only during October, 

 and it \\.i- taken in the ocean off Barnegat by Mayer during the 

 -.nne month. It is not stated at what depth these were obtained 

 nor i- the temperature given. As bearing on Bigelow's finding 

 that Pleurobrachia pileus and Mnemiopsis were mutually ex- 

 lu-i\ . it \\ ill be remembered that in the swarms observed by me 

 in the Mulliru River/*, brunnea and M. leidyi were taken together 

 in large numbers at the surface in water dipped up with a 

 fingerbowl. 



In i OIK lu-ion, consideration must be given to the part which 

 salinity and temperature play in the sporadic appearanre of the 

 three ctenophores discussed here. A study of all data relating to 

 rainfall, seasonal temperatures, severity of the preceding \\inter, 

 and other factors, fails to show any correlation between these and 

 the abundance of the ctenophores. The fact that one or t\\o 

 spri imen> of Mnemiopsis have been taken every year at \\ood- 

 Ilolr >in< e they ceased to be found there in abundance, and the 

 e of occasional specimens in Barnegat Bay even during 

 "off" \i-.irs, indicates that the factors controlling the appearance 

 of the ctenophores probably lie mainly outside the several 

 I-' ,ilitie> \\hich are considered in this paper. 



All ctenophores disappear from the shallow bays during the 

 \\inter, the waters being repopulated the following summer from 

 the -ea. Should the region in which Bigelow found Mnemiopsis 

 in >uch abundance in the Atlantic Ocean off the New Jersey coast 

 -hitied even a mile or two eastward during some years, it 

 \\ould probably pass beyond the influence of the tidal ebb and 

 ll< >\\ t hi < .ugh Barnegat Inlet and as a result few if any Mnemiopsis 

 \\onld In- found in the Bay. Long continued easterly winds do 

 biing to our shores forms which do not normally occur there but 

 the effects of such winds and the currents produced thereby are 

 doubt le-- onl\ temporary. 



\<> one knows the effects on the plankton of coastal waters 

 \\liirh re-tilt from even slight shifts in the direction, and of 

 chan-r- in temperature or of salinity of the larger oceanic 



