indicating the presence of the benzene ringo No positive test for 

 protein was given on layering the solution over concentrated nitric 

 acido The lead test for sxilphur was negativeo 



A series of ejtperiments was conducted to compare the 

 effects of precipitation by boiling and precipitation by salting out of 

 the proteins on the attractiveness of the filtrateo The procedure a:n.d 

 results are depicted m figure 80 Clear stock extract was boiled for 

 15 minutes and centrifuged; the centrifugate was divided into three 

 equal partSp the first of which was tested (NOo 85)0 the second of which 

 was saturated with sodium chloride;, centrifuged^ and both centrifugate 

 (Noso 8 3, 86) and residue (NOo 88) tested^ and the third of which was 

 boiled for an additional hour^ centrifuged^ and the centrifugate tested 

 (Noo 84>o Strong responses were obtained with all tests except that 

 with the residue (No„ 88)0 The attractant was not removed with pre- 

 cipitation in either boiling or saltmgo Apparently fractionation was 

 complete when both boiling amd salting were used (compare NoSo 83 

 and 86 with No^ 88^0 



The boiling ar.d salting procedure was carried one step 

 farther in two additional experiments „ The centrtfugate„ after boiling 

 and salting, was bo>led to a residue. When re-dissolved in seawater, 

 a positive response was obtained iNoSo HSj 121)o 



The possibility of precipitating or destroying the attract 

 tive substance by heat after it had been segregated in a relatively 

 pure (protein-free) state by dialysis was next investigatedo One liter 

 of the dialyzate from a stock extract was boiled to 10 mlo and tested^ 

 producing a very strong response (NOo 118)o The residue from dialy<= 

 SI8 was boiled to a gummy residue;, producing weaker but positive 

 responses with both the 95 percent alcohol soluble portions and the 

 alcohol insoluble portions (NoSo 114^ 115^ II6II0 In a second serieSj 

 the dialyzate was boiled to dryness and a strong positive response was 

 obtained with the portion of the residue which was soluble in absolute 

 ethyl alcohol (No, IZJK The solubility in absolute alcohol was con- 

 firmed m later experiments WoSo 201^ ?8Ho 



Thus the attractant is a substance comprised of a small 

 molecule which is (at leasts partly) soluble in absolute ethyl alcohol. 

 This property rules out most of the known amino acids (except nnethio- 

 nine and proline>o However^ that part of the attractant or attractants 

 was insoluble in alcohol yet soluble in water is indicated by several 

 experiments in which the alcohol^^insolubleo water -^ soluble portion 

 gave a positive response (NoSo 115p 116, 124^ I83\o 



Because of the time required for dialysis and the 

 incomplete sepciration that was achieved^ attention was directed at 



39 



