THE APPLICATION OF THE PRECIPITIN TECHNIQUE TO THEORIES CONCERNING THE ORIGIN OF VERTEBRATES

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Abstract
The precipitin reaction was applied to distantly related groups among the invertebrates and chordates to test the various theories concerning the origin of vertebrates. The spp. employed in the study were: Echinodermata[long dash]Asterias jorbesi, Arbacia punctulata, Echinarachnius parma, Leptosynapta inhaerens, Thyone briareus; Annelida[long dash]Arabella opalina, Chaetopterus pergamentaceus, Cirratulus grandis, Glycera dibranciata, Phascolosoma gouldi; Arthropoda[long dash]Limulus polyphemus; Chordata[long dash]Dolichoglossus kowalevskyi, Amaroucium constellatum, Molgula manhattensis, Styela partita. Consistent results, confirmed by reciprocal tests, were obtained by injn. of saline solns. (buffered to pH 7.3) containing 500 mg. of lyophilized anti-genic material from which the lipids had been removed. With 3 exceptions, the titer of homologous reactions was 1:1, 024,000 [plus or minus] 1 dilution tube, and heterologous titers never exceeded homologous ones. Titers of cross-reactions between members of the various invertebrate phyla and the Prochordata were, in general, much higher in the case of echinoderm-prochordate reactions (e.g., 1:4000, 1:8000) than in annelid-prochordate (highest, 1:400) or arthropod-pro-chordate (highest, 1:400) tests. The titers of reactions between annelid and arthropod materials were of the same order of magnitude as those between echinoderm and pro-chordate materials. Serologically, as well as morphologically and developmentally, the chordates are more closely related to the echinoderms than to any other group of invertebrates tested, indicating that chordates evolved from animals which also gave rise to present-day echinoderms.

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