Another problem is the sheer physical size of the water sample required to get any measurements at all. Up to now there has been no truly effective radiation counter that can be lowered over the side of a ship to the desired depth. It is often necessary to collect a sample of many gallons at great depths and return it to the surface without its being mixed by any of the intervening water. This is difficult at best, and only rather primitive methods have been developed. None is more than partly satisfactory. A standard system is to lower a large, collapsed polyethylene bag to the desired depth, open it, fill it, and close it again, all by remote control, and then gingerly and hopefully return it to the surface. Results do not always agree among samples taken at the same location by different methods or by different scientists. There is still no universal agreement among scientists as to the quantitative validity of any of the measurements, although as more and better data are gathered there tends to be a greater concurrence. [Illustration: _Fifty-gallon sampler ready to be lowered over the side of the research vessel_ Atlantis II _in the North Atlantic. Such devices are used to obtain samples at fixed intervals from the sea surface to the bottom. The water is analyzed for radioisotope content._] Recently, under an AEC contract, a detector for direct measurements of gamma radiation[9] in the deep ocean was developed for the Institute of Marine Sciences, University of Miami, by the Franklin GNO Corp. (See figure above.) This unit incorporates two of the largest plastic scintillation counters[10] ever used in the ocean—each is 16 inches in diameter by 12 inches thick. This apparatus may permit direct qualitative and quantitative measurement of radiation at great depths by techniques that will be eminently more satisfactory than water sampling. Already tests with the detector have disclosed the existence of cosmic-ray effects at much greater depths than heretofore known. [Illustration: _Scintillation counter for use in the deep ocean._] [Illustration: _Constituent parts. The plastic discs are the radiation detectors._] Biologists from Woods Hole Oceanographic Institution in Massachusetts for the first time have been able to measure the rate of excretion of physiologically important fallout radionuclides by several species of zooplankton—_pteropods_, _pyrasomes_, _copepods_, and _euphausids_. Radioactive zinc and iodine, it was learned, are excreted as soluble ions, while iron and manganese appear as solid particles. However, the extent to which the intake and excretion of radionuclides and the vertical migration of zooplankton contribute quantitatively to the transport of radioactivity across the thermocline (and into the ocean deeps) still can only be guessed.