IODINE IN MARINE FLORA AND FAUNA 65 



SESSIONAL PAPER No. 39b 



hypothesis is in line with Gautier's results for sea-water itself (}). He found that 

 sea-water obtained at the surface contained no inorganic iodine, but only organi- 

 cally combined iodine, and iodine present in minute organisms, while the greater 

 the depth from which the water was obtained the greater the amount of inorganic 

 iodine it contained (2). His results, rigorously applied, would indicate that the 

 algse themselves obtain their iodine in organic form. This is perhaps not absolutely 

 impossible, since various authors seem to have shown that algse can assimilate 

 organic material (s), including amino-acids (and as already pointed out at least 

 part of the iodine in organic combination is in amino-acid groups), but it seems 

 more probable that a minimal quantity of iodine reaches the inorganic stage, and 

 is then reabsorbed by the algae, so continuing the circulation. 



A conclusion which may fairly be drawn from the data now presented is that 

 with greater development in the organism is found greater specificity of iodine- 

 containing tissue, until, in vertebrates, the thyroid is the only organ containing 

 an appreciable amount. It is to be noted that in Squalus sucklii, the vertebiate 

 type under examination, the only other oigans in which iodine was detected were 

 excretory organs. 



Iodine has been found present in marked quantity in three different tissues 

 in which, as far as I am awaie, it has not previously been recorded. These are, 

 the homy tube secreted by the worm Diopatra, the cellulose ("tunicine") test of 

 the tunicate Pyura, and the external cuticle of the horse-clam Schizothoerus. 

 1 hope to examine these further, along with similar tissue in other species. 



There are at present insufScient data for any generalisation as to the type of 

 tissue containing iodine in relatively large amount, but it may be pointed out 

 that the iodine in thyroid tissue is usually regarded as localised in the colloid 

 material, which has been assumed — without experimental evidence — to consist 

 of or to contain a globulin (thyreoglobulin) , while the iodine in sponges is contained 

 in spongin, a sclero-protein, that in corals in gorgonin, also a sclero-protein, and 

 the organic substance of the serpulid tube is conchiolin, another sclero-protein. The 

 external cuticle of Schizothoerus probably consists largely of a keratin, yet another 

 sclero-protein. On the other hand, the organic material of at least one Eunicid 

 worm (Hyalinoecia) appears to consist of onuphin, which although containing 

 nitrogen seems closelj'- related to dextrin or glycogen (<), the test of tunicates 

 appears to consist largely of true cellulose (^) (which is easily caused to combine 



» Compt. rend., 1899, 128, 1069. 



« Ibid., 1899, 129, 9. 



» See Oltmann's "Morphologic und Biologie der Algen," 1905, Bd. 2, S. 155. 



* Schmiedeberg, Mitt. a. d. zool. Station zu Neapel, 1882, 3, 373. {\ote added to proof. 

 Sine- writi g th? ab:»vc, I have f und ai obs rvaiion of Tvlorn^r's (Zeitschr. f. physiol. Chem., 

 1908, 35, 83,) on th"^ pr SM^ce of iodine in th^ tubes (f the worms Hyalinoecia tubicola a d 

 Chaetopterus norvegicus Ih" amou ts ar ■ smaller, but of th^ sane order as hat I hav^ found 

 for Diopatra). 



" Cp. Winterstein, Zeitschr. f. physiol. Chem., 1894, 18, 43. 



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